Showing papers by "Richard S. Spielman published in 2002"

The genetics of variation in gene expression

Abstract: The genetic basis of variation in gene expression lends itself to investigation by microarrays. For genetic analysis, we view the expression level of a gene as a quantitative or 'complex' trait, analogous to an individual's height or cholesterol level, and, therefore, as an inherited phenotype. Several genetic analyses of 'gene expression phenotypes' have been carried out in experimental organisms, and initial steps have been taken toward similar studies in humans--although these present challenging technical and statistical problems. Further advances in the genetic analysis of variation in gene expression will contribute to our understanding of transcriptional regulation and will provide models for studying other quantitative and complex traits.

Gene Expression Phenotype in Heterozygous Carriers of Ataxia Telangiectasia

Abstract: The defining characteristic of recessive diseases is the absence of a phenotype in the heterozygous carriers. Nonetheless, subtle manifestations may be detectable by new methods, such as expression profiling. Ataxia telangiectasia (AT) is a typical recessive disease, and individual carriers cannot be reliably identified. As a group, however, carriers of an AT disease allele have been reported to have a phenotype that distinguishes them from normal control individuals: increased radiosensitivity and risk of cancer. We show here that the phenotype is also detectable, in lymphoblastoid cells from AT carriers, as changes in expression level of many genes. The differences are manifested both in baseline expression levels and in response to ionizing radiation. Our findings show that carriers of a recessive disease may have an "expression phenotype." In the particular case of AT, this suggests a new approach to the identification of carriers and enhances understanding of their increased cancer risk. More generally, we demonstrate that genomic technologies offer the opportunity to identify and study unaffected carriers, who are hundreds of times more common than affected patients.

Nuclear and mitochondrial genetic variation in the Yanomamö: A test case for ancient DNA studies of prehistoric populations

Abstract: Ancient DNA provides a potentially revolutionary way to study biological relationships in prehistoric populations, but genetic patterns are complex and require careful interpretation based on robust, well-tested models. In this study, nuclear and mitochondrial markers were compared in the Yanomamo, to assess how well each data set could differentiate among closely related groups. The villages selected for the study share a recent fission history and are closely related to each other, as would likely be the case among prehistoric peoples living in the same valley or region. The Yanomamo generally practice village-level endogamy, but some migration and gene flow are known to occur between villages. Nuclear and mitochondrial DNA data were compared using F-statistics and genetic distance analyses. The nuclear data performed as expected, males and females from the same village were similar, and the villages were genetically distinct, with the magnitude of genetic differences correlated with historical relationship. However, mtDNA analyses did not yield the expected results. The genetic distances between villages did not correlate with historical relationship, and the sexes were significantly different from each other in two villages. Both the Lane and Sublett and the Spence methods, used to test for archaeological residence patterns, were consistent with endogamy. Hence, ancient DNA can, in principle, provide us with a unique opportunity to study genetic structure and gene flow in archaeological populations. However, interpretations, particularly those based on single loci such as mitochondrial DNA, should be cautious because sex-specific migration and sampling issues may have dramatic effects.

Genetic analysis of candidate genes for the polycystic ovary syndrome

Abstract: The genetic analysis of polycystic ovary syndrome (PCOS) presents the typical problems associated with the inheritance of a common, complex disorder. Despite evidence for substantial familial aggregation of PCOS the mode of inheritance is uncertain, and no specific contributing genes have been confidently identified. However, materials and methods for testing candidate genes have recently been greatly enhanced by progress in the Human Genome Project. As a result, several genes and chromosomal regions that hold promise have emerged in recent studies of the genetics of PCOS. The authors review results for several candidate genes in detail and provide a catalogue of references and results for many other candidate genes and regions.

Linkage and association with type 1 diabetes on chromosome 1q42.

Abstract: Type 1 diabetes is a complex disorder with multiple genetic loci and environmental factors contributing to disease etiology. In the current study, a human type 1 diabetes candidate region on chromosome 1q42 was mapped at high marker density in a panel of 616 multiplex type 1 diabetic families. To facilitate the identification and evaluation of candidate genes, a physical map of the 7-cM region surrounding the maximum logarithm of odds (LOD) score (2.46, P = 0.0004) was constructed. Genes were identified in the 500-kb region surrounding the marker yielding the peak LOD score and evaluated for polymorphism by resequencing. Single-nucleotide polymorphisms (SNPs) identified in these genes as well as other anonymous markers were tested for allelic association with type 1 diabetes by both family-based and case-control methods. A haplotype formed by common alleles at three adjacent markers (D1S225, D1S2383, and D1S251) was preferentially transmitted to affected offspring in type 1 diabetic families (nominal P = 0.006). These findings extend the evidence supporting the existence of a type 1 diabetes susceptibility locus on chromosome 1q42 and identify a candidate region amenable to positional cloning efforts.