Genomic heterogeneity and instability of the AZF locus on the human Y chromosome.
TL;DR: A genetic redundancy of the multi-copy genes in AZFb and AZFc and a causative relationship between the occurrence of first microdeletions then macro deletions in the repetitive structure of Yq11 is suggested where large palindromes are probably promoting multiple gene conversions andAZF rearrangements.
About: This article is published in Molecular and Cellular Endocrinology.The article was published on 2004-09-30. It has received 88 citations till now. The article focuses on the topics: Azoospermia factor.
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TL;DR: The American College of Medical Genetics has developed the following professional guidelines for the interpretation and reporting of copy number variation: evaluation of constitutional copy number variants detected in the postnatal setting.
751 citations
TL;DR: A quantitative, evidence-based scoring framework is introduced; the implementation of the five-tier classification system widely used in sequence variant classification is encouraged; and “uncoupling” the evidence- based classification of a variant from its potential implications for a particular individual is recommended.
673 citations
TL;DR: The genetic causes of male infertility known to date, the genetic polymorphisms possibly associated with male infertility, and novel results of global gene expression profiling of normal human testis by microarray technology are reported.
Abstract: Male infertility represents one of the clearest examples of a complex disease with a substantial genetic basis. Numerous male mouse models, mutation screening and association studies reported over the last few years reveal the high prevalence of genetic causes of spermatogenic impairment, accounting for 10-15% of severe male infertility, including chromosomal aberrations and single gene mutations. Natural selection prevents the transmission of mutations causing infertility, but this protective mechanism may be overcome by assisted reproduction techniques. Consequently, the identification of genetic factors is important for appropriate management of the infertile couple. However, a large proportion of infertile males are diagnosed as idiopathic, reflecting poor understanding of the basic mechanisms regulating spermatogenesis and sperm function. Furthermore, the molecular mechanisms underlying spermatogenic damage in cases of genetic infertility (for example Yq microdeletions) are not known. These problems can be addressed only by large scale association studies and testicular or spermatozoal expression studies in well-defined alterations of spermatogenesis. It is conceivable that these studies will have important diagnostic and therapeutic implications in the future. This review discusses the genetic causes of male infertility known to date, the genetic polymorphisms possibly associated with male infertility, and reports novel results of global gene expression profiling of normal human testis by microarray technology.
418 citations
Cites background from "Genomic heterogeneity and instabili..."
...Therefore, AZF microdeletions can be considered as ‘pre-mutations’ for a subsequent complete loss of the Y chromosome in the AZF-deleted patients’ spermatozoa, increasing the risk of embryonic X0 cells (Vogt, 2004)....
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TL;DR: A systematic search of the nonrecombining region of the human Y chromosome (NRY) identified 12 novel genes or families, 10 with full-length complementary DNA sequences, which may account for infertility among men with Y deletions.
Abstract: A systematic search of the nonrecombining region of the human Y chromosome (NRY) identified 12 novel genes or families, 10 with full-length complementary DNA sequences. All 12 genes, and six of eight NRY genes or families previously isolated by less systematic means, fell into two classes. Genes in the first group were expressed in many organs; these housekeeping genes have X homologs that escape X inactivation. The second group, consisting of Y-chromosomal gene families expressed specifically in testes, may account for infertility among men with Y deletions. The coherence of the NRY's gene content contrasts with the apparently haphazard content of most eukaryotic chromosomes.
412 citations
Journal Article•
TL;DR: The current estimate is that about 30 percent of men seeking help at the infertility clinic are found to have oligozoospermia or azoospermia of unknown aetiology, and there is a need to find the cause of infertility.
Abstract: Infertility is defined as a failure to conceive in a couple trying to reproduce for a period of two years without conception. Approximately 15 percent of couples are infertile, and among these couples, male factor infertility accounts for approximately 50 percent of causes. Male infertility is a multifactorial syndrome encompassing a wide variety of disorders. In more than half of infertile men, the cause of their infertility is unknown (idiopathic) and could be congenital or acquired. Infertility in men can be diagnosed initially by semen analysis. Seminograms of infertile men may reveal many abnormal conditions, which include azoospermia, oligozoospermia, t e r at ozoos p e r mi a , a s t he nozoos p e r mi a , necrospermia and pyospermia. The current estimate is that about 30 percent of men seeking help at the infertility clinic are found to have oligozoospermia or azoospermia of unknown aetiology. Therefore, there is a need to find the cause of infertility. The causes are known in less than half of these cases, out of which genetic or inherited disease and specific abnormalities in the Y chromosome are major factors. About 10–20 percent of males presenting without sperm in the ejaculate carry a deletion of the Y chromosome. This deleted region includes the Azoospermia Factor (AZF) locus, located in the Yq11, which is divided into four recurrently deleted non-overlapping subregions designated as AZFa, AZFb, AZFc and AZFd. Each of these regions may be associated with a particular testicular histology, and several candidate genes have been found within these regions. The Deleted in Azoospermia (DAZ) gene family is reported to be the most frequently deleted AZF candidate gene and is located in the AZFc region. Recently, a partial, novel Y chromosome 1.6-Mb deletion, designated “gr/gr” deletion, has been described specifically in infertile men with varying degrees of spermatogenic failure. The DAZ gene has an autosomal homologue, DAZL (DAZ-Like), on the short arm of the chromosome 3 (3p24) and it is possible that a defective autosomal DAZL may be responsible for the spermatogenic defect. The genetic complexity of the AZF locus on the long arm of the Y chromosome could be revealed only with the development of sequence tagged sites. Random attacks on the naked mitochondrial DNA (mtDNA) of sperm by reactive oxygen species or free radicals will inevitably cause oxidative damage or mutation to the mitochondrial genome with pathological consequences and lead to infertility in males. The key nuclear enzyme involved in the elongation and repair of mtDNA strands is DNA polymerase gamma, mapped to the long arm of chromosome 15 (15q25), and includes a CAG repeat region. Its mutation affects the adenosine triphosphate production. The introduction of molecular techniques has provided great insight into the genetics of infertility. Yet, our understanding of the genetic causes of male infertility remains limited.
328 citations
References
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TL;DR: A simple set of rules was developed to unambiguously label the different clades nested within a single most parsimonious phylogeny, which supersedes and unifies past nomenclatures and allows the inclusion of additional mutations and haplogroups yet to be discovered.
Abstract: The Y chromosome contains the largest nonrecombining block in the human genome. By virtue of its many polymorphisms, it is now the most informative haplotyping system, with applications in evolutionary studies, forensics, medical genetics, and genealogical reconstruction. However, the emergence of several unrelated and nonsystematic nomenclatures for Y-chromosomal binary haplogroups is an increasing source of confusion. To resolve this issue, 245 markers were genotyped in a globally representative set of samples, 74 of which were males from the Y Chromosome Consortium cell line repository. A single most parsimonious phylogeny was constructed for the 153 binary haplogroups observed. A simple set of rules was developed to unambiguously label the different clades nested within this tree. This hierarchical nomenclature system supersedes and unifies past nomenclatures and allows the inclusion of additional mutations and haplogroups yet to be discovered.
797 citations
TL;DR: A systematic search of the nonrecombining region of the human Y chromosome (NRY) identified 12 novel genes or families, 10 with full-length complementary DNA sequences, which may account for infertility among men with Y deletions.
Abstract: A systematic search of the nonrecombining region of the human Y chromosome (NRY) identified 12 novel genes or families, 10 with full-length complementary DNA sequences. All 12 genes, and six of eight NRY genes or families previously isolated by less systematic means, fell into two classes. Genes in the first group were expressed in many organs; these housekeeping genes have X homologs that escape X inactivation. The second group, consisting of Y-chromosomal gene families expressed specifically in testes, may account for infertility among men with Y deletions. The coherence of the NRY's gene content contrasts with the apparently haphazard content of most eukaryotic chromosomes.
771 citations
"Genomic heterogeneity and instabili..." refers methods in this paper
...Based on the knowledge of the Y-chromosomal sequence and extensive testis cDNA screening programs (Lahn and Page, 1997; Vogt et al., 1997; Kuroda-Kawaguchi et al., 2001), AZFb contains eight protein-coding genes (CDY2, EIF1AY, HSFY, PRY, RBMY1, RPS4Y2, SMCY, XKRY) and AZFc five protein-coding genes…...
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TL;DR: The complete nucleotide sequence of AZFc was determined by identifying and distinguishing between near-identical amplicons (massive repeat units) using an iterative mapping–sequencing process.
Abstract: Deletions of the AZFc (azoospermia factor c) region of the Y chromosome are the most common known cause of spermatogenic failure. We determined the complete nucleotide sequence of AZFc by identifying and distinguishing between near-identical amplicons (massive repeat units) using an iterative mapping-sequencing process. A complex of three palindromes, the largest spanning 3 Mb with 99.97% identity between its arms, encompasses the AZFc region. The palindromes are constructed from six distinct families of amplicons, with unit lengths of 115-678 kb, and may have resulted from tandem duplication and inversion during primate evolution. The palindromic complex contains 11 families of transcription units, all expressed in testis. Deletions of AZFc that cause infertility are remarkably uniform, spanning a 3.5-Mb segment and bounded by 229-kb direct repeats that probably served as substrates for homologous recombination.
626 citations
TL;DR: A deletion map of the human Y chromosome was constructed by testing 96 individuals with partial Y chromosomes for the presence or absence of many DNA loci, and should be useful in identifying Y chromosomal genes, in exploring the origin of chromosomal disorders, and in tracing the evolution of the Y chromosome.
Abstract: A deletion map of the human Y chromosome was constructed by testing 96 individuals with partial Y chromosomes for the presence or absence of many DNA loci. The individuals studied included XX males, XY females, and persons in whom chromosome banding had revealed translocated, deleted, isodicentric, or ring Y chromosomes. Most of the 132 Y chromosomal loci mapped were sequence-tagged sites, detected by means of the polymerase chain reaction. These studies resolved the euchromatic region (short arm, centromere, and proximal long arm) of the Y chromosome into 43 ordered intervals, all defined by naturally occurring chromosomal breakpoints and averaging less than 800 kilobases in length. This deletion map should be useful in identifying Y chromosomal genes, in exploring the origin of chromosomal disorders, and in tracing the evolution of the Y chromosome.
492 citations
TL;DR: A small proportion of men with infertility have Y-chromosome microdeletions, but the size and position of the deletions correlate poorly with the severity of spermatogenic failure, and a deletion does not preclude the presence of viable sperm and possible conception.
Abstract: Background Some infertile men with azoospermia or severe oligospermia have small deletions in regions of the Y chromosome. However, the frequency of such microdeletions among men with infertility in general is unknown. We sought to determine the prevalence of Y-chromosome microdeletions among infertile men and to correlate the clinical presentation of the men with specific deletions. Methods We studied 200 consecutive infertile men. Each man was evaluated comprehensively for known causes of infertility, and Y-chromosome microdeletions were studied with use of the polymerase chain reaction to amplify specific regions of the chromosome. The Y chromosomes of 200 normal men were also analyzed. Results Fourteen infertile men (7 percent) and four normal men (2 percent) had microdeletions of the Y chromosome. Nine of the infertile men had azoospermia or severe oligospermia (sperm concentration, <5 million per milliliter), four had oligospermia (sperm concentration, 5 million to <20 million per milliliter), and one had normospermia (sperm concentration, ≥20 million per milliliter). The size and location of the deletions varied and did not correlate with the severity of spermatogenic failure. The fathers of six infertile men with microdeletions were studied; two had the same deletions as their sons, and four had no deletions. Conclusions A small proportion of men with infertility have Y-chromosome microdeletions, but the size and position of the deletions correlate poorly with the severity of spermatogenic failure, and a deletion does not preclude the presence of viable sperm and possible conception.
432 citations