Showing papers in "Nature Genetics in 1995"
TL;DR: This work has identified a common mutation in MTHFR which alters a highly-conserved amino acid; the substitution occurs at a frequency of approximately 38% of unselected chromosomes and may represent an important genetic risk factor in vascular disease.
Abstract: Hyperhomocysteinaemia has been identified as a risk factor for cerebrovascular, peripheral vascular and coronary heart disease. Elevated levels of plasma homocysteine can result from genetic or nutrient-related disturbances in the trans-sulphuration or re-methylation pathways for homocysteine metabolism. 5, 10-Methylenetetrahydrofolate reductase (MTHFR) catalyzes the reduction of 5, 10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, the predominant circulatory form of folate and carbon donor for the re-methylation of homocysteine to methionine. Reduced MTHFR activity with a thermolabile enzyme has been reported in patients with coronary and peripheral artery disease. We have identified a common mutation in MTHFR which alters a highly-conserved amino acid; the substitution occurs at a frequency of approximately 38% of unselected chromosomes. The mutation in the heterozygous or homozygous state correlates with reduced enzyme activity and increased thermolability in lymphocyte extracts; in vitro expression of a mutagenized cDNA containing the mutation confirms its effect on thermolability of MTHFR. Finally, individuals homozygous for the mutation have significantly elevated plasma homocysteine levels. This mutation in MTHFR may represent an important genetic risk factor in vascular disease.
5,606 citations
TL;DR: Specific standards designed to maintain rigor while also promoting communication are proposed for the interpretation of linkage results in genetic studies under way for many complex traits.
Abstract: Genetic studies are under way for many complex traits, spurred by the recent feasibility of whole genome scans. Clear guidelines for the interpretation of linkage results are needed to avoid a flood of false positive claims. At the same time, an overly cautious approach runs the risk of causing true hints of linkage to be missed. We address this problem by proposing specific standards designed to maintain rigor while also promoting communication.
5,317 citations
TL;DR: Cytochemical analysis revealed a severe reduction in succinate dehydrogenase and aconitase activities in the heart and, to a lesser extent, in other organs, which indicates that MnSOD is required for normal biological function of tissues by maintaining the integrity of mitochondrial enzymes susceptible to direct inactivation by superoxide.
Abstract: The Sod2 gene for Mn-superoxide dismutase (MnSOD), an intramitochondrial free radical scavenging enzyme that is the first line of defense against superoxide produced as a byproduct of oxidative phosphorylation, was inactivated by homologous recombination. Homozygous mutant mice die within the first 10 days of life with a dilated cardiomyopathy, accumulation of lipid in liver and skeletal muscle, and metabolic acidosis. Cytochemical analysis revealed a severe reduction in succinate dehydrogenase (complex II) and aconitase (a TCA cycle enzyme) activities in the heart and, to a lesser extent, in other organs. These findings indicate that MnSOD is required for normal biological function of tissues by maintaining the integrity of mitochondrial enzymes susceptible to direct inactivation by superoxide.
1,745 citations
TL;DR: This work has identified a similar molecular mechanism in vivo for endocrine treatment failure in human prostate cancer which involves amplification of the androgen receptor (AR) gene.
Abstract: Overexpression of amplified genes is often associated with the acquisition of resistance to cancer therapeutic agents in vitro. We have identified a similar molecular mechanism in vivo for endocrine treatment failure in human prostate cancer which involves amplification of the androgen receptor (AR) gene. Comparative genomic hybridization shows that amplification of the Xq11-q13 region (the location), is common in tumours recurring during androgen deprivation therapy. We found high-level AR amplification in seven of 23 (30%) recurrent tumours, but in none of the specimens taken from the same patients prior to therapy. Our results suggest that AR amplification emerges during androgen deprivation therapy by facilitating tumour cell growth in low androgen concentrations.
1,489 citations
TL;DR: The region contains a single–copy gene, DAZ (Deleted in AZoospermia), which is transcribed in the adult testis and appears to encode an RNA binding protein, and the possibility that DAZ is AZF should now be explored.
Abstract: We have detected deletions of portions of the Y chromosome long arm in 12 of 89 men with azoospermia (no sperm in semen). No Y deletions were detected in their male relatives or in 90 other fertile males. The 12 deletions overlap, defining a region likely to contain one or more genes required for spermatogenesis (the Azoospermia Factor, AZF). Deletion of the AZF region is associated with highly variable testicular defects, ranging from complete absence of germ cells to spermatogenic arrest with occasional production of condensed spermatids. We find no evidence of YRRM genes, recently proposed as AZF candidates, in the AZF region. The region contains a single–copy gene, DAZ (Deleted in AZoospermia), which is transcribed in the adult testis and appears to encode an RNA binding protein. The possibility that DAZ is AZF should now be explored.
1,133 citations
TL;DR: A missense mutation that replaces serine with phenylalanine at codon 248, a strongly conserved amino acid residue in the second transmembrane domain is found in all 21 available affected family members and in four obligate carriers, but not in 333 healthy control subjects.
Abstract: Epilepsy affects at least 2% of the population at some time in their lives. The epilepsies are a heterogeneous group of disorders, many with an inherited component. Although specific genes have been identified in a few rare diseases causing seizures as part of a more diffuse brain disorder, the molecular pathology of the common idiopathic epilepsies is still unknown. Linkage has been reported for some generalised epilepsy syndromes, but only very recently for familial partial epilepsy syndromes. Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) is a partial epilepsy causing frequent, violent, brief seizures at night, usually beginning in childhood. The gene for ADNFLE maps to chromosome 20q13.2-q13.3 in one large Australian kindred. The neuronal nicotinic acetylcholine receptor alpha 4 subunit (CHRNA4) maps to the same region of 20q (ref. 12) and the gene is expressed in all layers of the frontal cortex. We screened affected family members for mutations within CHRNA4 and found a missense mutation that replaces serine with phenylalanine at codon 248, a strongly conserved amino acid residue in the second transmembrane domain. The mutation is present in all 21 available affected family members and in four obligate carriers, but not in 333 healthy control subjects.
1,048 citations
TL;DR: This study demonstrates an essential function for TGF–β3 in the normal morphogenesis of palate and lung, and directly implicates this cytokine in mechanisms of epithelial–mesenchymal interaction.
Abstract: A broad spectrum of biological activities has been proposed for transforming growth factor-beta 3 (TGF-beta 3). To study TGF-beta 3 function in development, TGF-beta 3 null mutant mice were generated by gene-targeting. Within 20 hours of birth, homozygous TGF-beta 3-/- mice die with unique and consistent phenotypic features including delayed pulmonary development and defective palatogenesis. Unlike other null mutants with cleft palate, TGF-beta 3-/- mice lack other concomitant craniofacial abnormalities. This study demonstrates an essential function for TGF-beta 3 in the normal morphogenesis of palate and lung, and directly implicates this cytokine in mechanisms of epithelial-mesenchymal interaction.
1,035 citations
TL;DR: Intragenic non–overlapping deletions from four different families and three mutations have been detected in HYP patients, which suggest that the PEX gene is involved in the HYP disorder.
Abstract: X–linked hypophosphatemic rickets (HYP) is a dominant disorder characterised by impaired phosphate uptake in the kidney, which is likely to be caused by abnormal regulation of sodium phosphate cotransport in the proximal tubules. By positional cloning, we have isolated a candidate gene from the HYP region in Xp22.1. This gene exhibits homology to a family of endopeptidase genes, members of which are involved in the degradation or activation of a variety of peptide hormones. This gene (which we have called PEX) is composed of multiple exons which span at least five cosmids. Intragenic non–overlapping deletions from four different families and three mutations (two splice sites and one frameshift) have been detected in HYP patients, which suggest that the PEX gene is involved in the HYP disorder.
997 citations
TL;DR: The findings suggest that in humans, as in other mammals, the MC1R is a control point in the regulation of pigmentation phenotype and, more importantly, that variations in this protein are associated with a poor tanning response.
Abstract: Melanin pigmentation protects the skin from the damaging effects of ultraviolet radiation (UVR). There are two types of melanin, the red phaeomelanin and the black eumelanin, both of which are present in human skin. Eumelanin is photoprotective whereas phaeomelanin, because of its potential to generate free radicals in response to UVR, may contribute to UV-induced skin damage. Individuals with red hair have a predominance of phaeomelain in hair and skin and/or a reduced ability to produce eumelanin, which may explain why they fail to tan and are at risk from UVR. In mammals the relative proportions of phaeomelanin and eumelanin are regulated by melanocyte stimulating hormone (MSH), which acts via its receptor (MC1R), on melanocytes, to increase the synthesis of eumelanin and the product of the agouti locus which antagonises this action. In mice, mutations at either the MC1R gene or agouti affect the pattern of melanogenesis resulting in changes in coat colour. We now report the presence of MC1R gene sequence variants in humans. These were found in over 80% of individuals with red hair and/or fair skin that tans poorly but in fewer than 20% of individuals with brown or black hair and in less than 4% of those who showed a good tanning response. Our findings suggest that in humans, as in other mammals, the MC1R is a control point in the regulation of pigmentation phenotype and, more importantly, that variations in this protein are associated with a poor tanning response.
929 citations
TL;DR: In this article, the reproducibility of this phenotype among mice with segmental trisomy 16 (Ts65Dn mice) indicates that dosage imbalance for a gene or genes in this region contributes to this impairment.
Abstract: Trisomy 21 or Down syndrome (DS) is the most frequent genetic cause of mental retardation, affecting one in 800 live born human beings. Mice with segmental trisomy 16 (Ts65Dn mice) are at dosage imbalance for genes corresponding to those on human chromosome 21q21-22.3--which includes the so-called DS 'critical region'. They do not show early-onset of Alzheimer disease pathology; however, Ts65Dn mice do demonstrate impaired performance in a complex learning task requiring the integration of visual and spatial information. The reproducibility of this phenotype among Ts65Dn mice indicates that dosage imbalance for a gene or genes in this region contributes to this impairment. The corresponding dosage imbalance for the human homologues of these genes may contribute to cognitive deficits in DS.
874 citations
TL;DR: Gene targeting was used to generate mice with a null allele of the gene involved in X–linked CGD, which encodes the 91 kD subunit of the oxidase cytochrome b, and affected hemizygous male mice lacked phagocyte superoxide production and had an altered inflammatory response in thioglycollate peritonitis.
Abstract: Chronic granulomatous disease (CGD) is a recessive disorder characterized by a defective phagocyte respiratory burst oxidase, life-threatening pyogenic infections and inflammatory granulomas. Gene targeting was used to generate mice with a null allele of the gene involved in X-linked CGD, which encodes the 91 kD subunit of the oxidase cytochrome b. Affected hemizygous male mice lacked phagocyte superoxide production, manifested an increased susceptibility to infection with Staphylococcus aureus and Aspergillus fumigatus and had an altered inflammatory response in thioglycollate peritonitis. This animal model should aid in developing new treatments for CGD and in evaluating the role of phagocyte-derived oxidants in inflammation.
TL;DR: The results indicate that polycystin is an integral membrane protein involved in cell–cell/matrix interactions and not the duplicate loci of polycystic kidney disease 1.
Abstract: Characterization of the polycystic kidney disease 1 (PKD1) gene has been complicated by genomic rearrangements on chromosome 16. We have used an exon linking strategy, taking RNA from a cell line containing PKD1 but not the duplicate loci, to clone a cDNA contig of the entire transcript. The transcript consists of 14,148 bp (including a correction to the previously described C terminus), distributed among 46 exons spanning 52 kb. The predicted PKD1 protein, polycystin, is a glycoprotein with multiple transmembrane domains and a cytoplasmic C-tail. The N–terminal extracellular region of over 2,500 aa contains leucine–rich repeats, a C–type lectin, 16 immunoglobulin–like repeats and four type III fibronectin–related domains. Our results indicate that polycystin is an integral membrane protein involved in cell–cell/matrix interactions.
TL;DR: This result demonstrates that TGF–β3 affects palatal shelf fusion by an intrinsic, primary mechanism rather than by effects secondary to craniofacial defects.
Abstract: Mice lacking TGF-beta 3 exhibit an incompletely penetrant failure of the palatal shelves to fuse leading to cleft palate. The defect appears to result from impaired adhesion of the apposing medial edge epithelia of the palatal shelves and subsequent elimination of the mid-line epithelial seam. No craniofacial abnormalities were observed. This result demonstrates that TGF-beta 3 affects palatal shelf fusion by an intrinsic, primary mechanism rather than by effects secondary to craniofacial defects.
TL;DR: Specific missense substitutions involving adjacent amino acids (Ser252Trp and Pro253Arg) in the linker between the second and third extracellular immunoglobulin domains of fibroblast growth factor receptor 2 (FGFR2) in all 40 unrelated cases of Apert syndrome are identified.
Abstract: Apert syndrome is a distinctive human malformation comprising craniosynostosis and severe syndactyly of the hands and feet. We have identified specific missense substitutions involving adjacent amino acids (Ser252Trp and Pro253Arg) in the linker between the second and third extracellular immunoglobulin (Ig) domains of fibroblast growth factor receptor 2 (FGFR2) in all 40 unrelated cases of Apert syndrome studied. Crouzon syndrome, characterized by craniosynostosis but normal limbs, was previously shown to result from allelic mutations of the third Ig domain of FGFR2. The contrasting effects of these mutations provide a genetic resource for dissecting the complex effects of signal transduction through FGFRs in cranial and limb morphogenesis.
TL;DR: This work proposes that huntingtin is involved in processes counterbalancing the operation of an apoptotic pathway, and shows that this protein is functionally indispensable for nullizygous embryos become developmentally retarded and disorganized, and die between days 8.5 and 10.5 of gestation.
Abstract: The expansion of CAG triplet repeats in the translated region of the human HD gene, encoding a protein (huntingtin) of unknown function, is a dominant mutation leading to manifestation of Huntington's disease. Targeted disruption of the homologous mouse gene (Hdh), to examine the normal role of huntingtin, shows that this protein is functionally indispensable, since nullizygous embryos become developmentally retarded and disorganized, and die between days 8.5 and 10.5 of gestation. Based on the observation that the level of the regionalized apoptotic cell death in the embryonic ectoderm, a layer expressing the Hdh gene, is much higher than normal in the null mutants, we propose that huntingtin is involved in processes counterbalancing the operation of an apoptotic pathway.
TL;DR: The results demonstrate that tumours can acquire somatic mutations that presumably do not directly affect cell growth but result only in genetic instability and suggest that many sporadic tumours with microsatellite instability have alterations in genes other than the four now known to participate in MMR.
Abstract: Microsatellite instability has been observed in both sporadic and hereditary forms of colorectal cancer. In the hereditary form, this instability is generally due to germline mutations in mismatch repair (MMR) genes. However, only one in ten patients with sporadic tumours exhibiting microsatellite instability had a detectable germline mutation. Moreover, only three of seven sporadic tumour cell lines with microsatellite instability had mutations in a MMR gene, and these mutations could occur somatically. These results demonstrate that tumours can acquire somatic mutations that presumably do not directly affect cell growth but result only in genetic instability. They also suggest that many sporadic tumours with microsatellite instability have alterations in genes other than the four now known to participate in MMR.
TL;DR: Although it is shown that the insulin gene is expressed biallelically in the adult pancreas, it is presented preliminary evidence that the level of transcription in vivo is correlated with allelic variation within the VNTR.
Abstract: The IDDM2 locus encoding susceptibility to type 1 diabetes was mapped previously to a 41-kb region spanning the insulin gene and a minisatellite or variable number of tandem repeats (VNTR) locus on human chromosome 11p155 By 'cross-match' haplotype analysis and linkage disequilibrium mapping, we have mapped the mutation IDDM2 to within the VNTR itself Other polymorphisms were systematically excluded as primary disease determinants Transmission of IDDM2 may be influenced by parent-of-origin phenomena Although we show that the insulin gene is expressed biallelically in the adult pancreas, we present preliminary evidence that the level of transcription in vivo is correlated with allelic variation within the VNTR Allelic variation at VNTRs may play an important general role in human disease
TL;DR: Genetic heterogeneity of Liddle's syndrome is demonstrated, independent roles of β and γ subunits in the negative regulation of channel activity are indicated, and a new gene in which mutation causes a salt–sensitive form of human hypertension is identified.
Abstract: Sensitivity of blood pressure to dietary salt is a common feature in subjects with hypertension. These features are exemplified by the mendelian disorder, Liddle's syndrome, previously shown to arise from constitutive activation of the renal epithelial sodium channel due to mutation in the β subunit of this channel. We now demonstrate that this disease can also result from a mutation truncating the carboxy terminus of the γ subunit of this channel; this truncated subunit also activates channel activity. These findings demonstrate genetic heterogeneity of Liddle's syndrome, indicate independent roles of β and γ subunits in the negative regulation of channel activity, and identify a new gene in which mutation causes a salt–sensitive form of human hypertension.
TL;DR: It is shown that the Duffy antigen/chemokine receptor gene (DARC) is composed of a single exon and that most Duffy–negative blacks carry a silent FY*B allele with a single T to C substitution at nucleotide −46.
Abstract: The mRNA for the Duffy blood group antigen, the erythrocyte receptor for the Plasmodium vivax malaria parasite, has recently been cloned and shown to encode a widely expressed chemokine receptor. Here, we show that the Duffy antigen/chemokine receptor gene (DARC) is composed of a single exon and that most Duffy–negative blacks carry a silent FY*B allele with a single T to C substitution at nucleotide −46. This mutation impairs the promoter activity in erythroid cells by disrupting a binding site for the GATA1 erythroid transcription factor. With the recent characterization of the FY*A and FY*B alleles, these findings provide the molecular basis of the Duffy blood group system and an explanation for the erythroid–speeific repression of the DARC gene in Duffy–negative individuals.
TL;DR: The fat mutation represents the first demonstration of an obesity–diabetes syndrome elicited by a genetic defect in a prohormone processing pathway.
Abstract: Mice homozygous for the fat mutation develop obesity and hyperglycaemia that can be suppressed by treatment with exogenous insulin. The fat mutation maps to mouse chromosome 8, very close to the gene for carboxypeptidase E (Cpe), which encodes an enzyme (CPE) that processes prohormone intermediates such as proinsulin. We now demonstrate a defect in proinsulin processing associated with the virtual absence of CPE activity in extracts of fat/fat pancreatic islets and pituitaries. A single Ser202Pro mutation distinguishes the mutant Cpe allele, and abolishes enzymatic activity in vitro. Thus, the fat mutation represents the first demonstration of an obesity-diabetes syndrome elicited by a genetic defect in a prohormone processing pathway.
TL;DR: A mutation in the nuclear–encoded flavoprotein (Fp) subunit gene of the succinate dehydrogenase (SDH) is reported in two siblings with complex II deficiency presenting as Leigh syndrome, the first report of a nuclear gene mutation causing a mitochondrial respiratory chain deficiency in humans.
Abstract: We now report a mutation in the nuclear-encoded flavoprotein (Fp) subunit gene of the succinate dehydrogenase (SDH) in two siblings with complex II deficiency presenting as Leigh syndrome. Both patients were homozygous for an Arg554Trp substitution in the Fp subunit. Their parents (first cousins) were heterozygous for the mutation that occurred in a conserved domain of the protein and was absent from 120 controls. The deleterious effect of the Arg to Trp substitution on the catalytic activity of SDH was observed in a SDH- yeast strain transformed with mutant Fp cDNA. The Fp subunit gene is duplicated in the human genome (3q29; 5p15), with only the gene on chromosome 5 expressed in human-hamster somatic cell hybrids. This is the first report of a nuclear gene mutation causing a mitochondrial respiratory chain deficiency in humans.
TL;DR: The expression pattern and chromosomal location of Sox9 suggest that it may be the gene defective in the mouse skeletal mutant Tail–short, a potential animal model for campomelic dysplasia.
Abstract: Mutations in the human SRY-related gene, SOX9, located on chromosome 17, have recently been associated with the sex reversal and skeletal dysmorphology syndrome, campomelic dysplasia. In order to clarify the role of this gene in skeletal development, we have studied the expression of mouse Sox9 during embryogenesis. Sox9 is expressed predominantly in mesenchymal condensations throughout the embryo before and during the deposition of cartilage, consistent with a primary role in skeletal formation. Interspecific backcross mapping has localized mouse Sox9 to distal chromosome 11. The expression pattern and chromosomal location of Sox9 suggest that it may be the gene defective in the mouse skeletal mutant Tail-short, a potential animal model for campomelic dysplasia.
TL;DR: It is found that small homozygous deletions represent the predominant mechanism of inactivation at 9p21 in bladder tumours and are present in other tumour types, including breast and prostate cancer.
Abstract: Many tumour types have been reported to have deletion of 9p21 (refs 1-6). A candidate target suppressor gene, p16 (p16INK4a/MTS-1/CDKN2), was recently identified within the commonly deleted region in tumour cell lines. An increasing and sometimes conflicting body of data has accumulated regarding the frequency of homozygous deletion and the importance of p16 in primary tumours. We tested 545 primary tumours by microsatellite analysis with existing and newly cloned markers around the p16 locus. We have now found that small homozygous deletions represent the predominant mechanism of inactivation at 9p21 in bladder tumours and are present in other tumour types, including breast and prostate cancer. Moreover, fine mapping of these deletions implicates a 170 kb minimal region that includes p16 and excludes p15.
TL;DR: The results suggest that one in a hundred women of Ashkenazi descent may be at especially high risk of developing breast and/or ovarian cancer.
Abstract: Since BRCA1, the first major gene responsible for inherited breast cancer, was cloned1, more than 50 unique mutations have been detected in the germline of individuals with breast and ovarian cancer1‐10. In high-risk pedigrees, female carriers of BRCA1 mutations have an 80–90% lifetime risk of breast cancer11, and a 40–50% risk of ovarian cancer12. However, the mutation status of individuals unselected for breast or ovarian cancer has not been determined, and it is not known whether mutations in such individuals confer the same risk of cancer as in individuals from the high-risk families studied so far. Following the finding of a 185delAG frameshift mutation in several Ashkenazi Jewish breast/ovarian families8,9,13, we have determined the frequency of this mutation in 858 Ashkenazim seeking genetic testing for conditions unrelated to cancer, and in 815 reference individuals not selected for ethnic origin. We observed the 185delAG mutation in 0.9% of Ashkenazim (95% confidence limit, 0.4%–1.8%) and in none of the reference samples. Our results suggest that one in a hundred women of Ashkenazi descent may be at especially high risk of developing breast and/or ovarian cancer.
TL;DR: Mice heterozygous for the GATA3 mutation are fertile and appear in all respects to be normal, whereas homozygous mutant embryos die between days 11 and 12 postcoitum (p.c.) and display massive internal bleeding, marked growth retardation, severe deformities of the brain and spinal cord, and gross aberrations in fetal liver haematopoiesis.
Abstract: GATA-3 is one member of a growing family of related transcription factors which share a strongly conserved expression pattern in all vertebrate organisms. In order to elucidate GATA-3 function using a direct genetic approach, we have disrupted the murine gene by homologous recombination in embryonic stem cells. Mice heterozygous for the GATA3 mutation are fertile and appear in all respects to be normal, whereas homozygous mutant embryos die between days 11 and 12 postcoitum (p.c.) and display massive internal bleeding, marked growth retardation, severe deformities of the brain and spinal cord, and gross aberrations in fetal liver haematopoiesis.
TL;DR: The positional candidate approach, which combines knowledge of map position with the increasingly dense human transcript map, greatly expedites the search process and will soon become the predominant method of disease gene discovery.
Abstract: The technique of positional cloning has become a familiar component of modern human genetics research. After a halting start in the mid-1980s, the number of disease genes succumbing to cloning efforts based solely on pinpointing their position in the genome is growing exponentially. More than 40 genes have been identified so far. But the positional candidate approach, which combines knowledge of map position with the increasingly dense human transcript map, greatly expedites the search process and will soon become the predominant method of disease gene discovery. The challenge ahead is to apply such methods to identifying genes involved in complex polygenic disorders.
TL;DR: In this article, a single nucleotide deletion in exon five caused a frame shift of the PAX2 coding region in the octapeptide domain, causing a mutation that resulted in a phenotype similar to Krd mutant mice.
Abstract: Paired box (PAX) genes play a critical role in human development and disease. The PAX2 gene is expressed in primitive cells of the kidney, ureter, eye, ear and central nervous system. We have conducted a mutational analysis of PAX2 in a family with optic nerve colobomas, renal hypoplasia, mild proteinuria and vesicoureteral reflux. We report a single nucleotide deletion in exon five, causing a frame-shift of the PAX2 coding region in the octapeptide domain. The phenotype resulting from the PAX2 mutation in this family was very similar to abnormalities that have been reported in Krd mutant mice. These data suggest that PAX2 is required for normal kidney and eye development.
TL;DR: The gene encoding the kidney isozyme of 11βHSD is analysed and mutations on both alleles in nine of 11 AME patients (eight of nine kindreds) markedly affect enzymatic activity and permit cortisol to occupy the renal mineralocorticoid receptor and thereby cause sodium retention and hypertension.
Abstract: The syndrome of apparent mineralocorticoid excess (AME) is an inherited form of human hypertension thought to result from a deficiency of 11 beta-hydroxysteroid dehydrogenase (11 beta HSD). This enzyme normally converts cortisol to inactive cortisone and is postulated to thus confer specificity for aldosterone upon the mineralocorticoid receptor. We have analysed the gene encoding the kidney isozyme of 11 beta HSD and found mutations on both alleles in nine of 11 AME patients (eight of nine kindreds). These mutations markedly affect enzymatic activity. They thus permit cortisol to occupy the renal mineralocorticoid receptor and thereby cause sodium retention and hypertension.
TL;DR: A small animal model of Haemophilia A is desirable for studies of factor VIII function and gene therapy, and a mouse with severe factorVIII deficiency is made using gene targeting.
Abstract: Haemophilia A is a classic X-linked disease which affects 1 in 5-10,000 males in all populations and is caused by defects in coagulation factor VIII. Roughly 60% of patients have severe disease with factor VIII activity < 1% of normal; they have frequent spontaneous bleeding into joints, soft tissues, muscles and internal organs. These patients usually require regular injections of plasma-derived or recombinant human factor VIII. Because this is expensive and can potentially lead to life-threatening complications, other forms of therapy, including gene therapy, have been proposed. Natural canine models of factor VIII and factor IX deficiency have been available for many years, and gene therapy attempts on these dogs have met with partial success. However, a small animal model of the disease is desirable for studies of factor VIII function and gene therapy. Using gene targeting, we have made a mouse with severe factor VIII deficiency.