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Peroxisome proliferator activated receptor gamma (PPARgamma) is a nuclear hormone receptor that has been shown to regulate differentiation and cell growth. Studies of the differentiative effects of PPARgamma agonists on several cancer cell lines led to the hypothesis that dysfunction of PPARgamma contributes to tumorigenesis. These functional observations were strengthened by genetic evidence: somatic loss-of-function mutations in PPARG, encoding PPARgamma, in sporadic colorectal carcinomas and somatic translocation of PAX8 and PPARG in follicular thyroid carcinoma. Recently overrepresentation of the H449H variant was found in a cohort of American patients with glioblastoma multiforme. The glioblastoma multiforme data suggest that PPARG contributes common, low-penetrance alleles for cancer susceptibility. To test this hypothesis in a broader range of cancers we examined a series of carcinomas of the cervix, endometrium, ovary, prostate, and kidney for germline sequence variation in PPARG. In addition to the two common sequence variants, P12A and H449H, there were five other sequence variants. P12A alleles were underrepresented in renal cell carcinoma patients compared to country-of-origin race-matched controls (3.75% vs. 12.1%, P<0.04). In contrast, the H449H variant was overrepresented in individuals with endometrial carcinoma compared to controls (14.4% vs. 6.25%, P<0.02). These observations lend genetic evidence consistent with our hypothesis that PPARG serves as a common, low-penetrance susceptibility gene for cancers of several types, especially those epidemiologically associated with obesity and fat intake.

We have analyzed the survival motor neuron gene (SMN1) dosage in 100 parents of children with homozygous SMN1 deletions. Of these parents, 96 (96%) demonstrated the expected one-copy SMN1 carrier genotype. However, four parents (4%) were observed to have a normal two-copy SMN1 dosage. The presence of two intact SMN1 genes in the parent of an affected child indicates either the occurrence of a de novo mutation event or a situation in which one chromosome has two copies of SMN1, whereas the other is null. We have separated individual chromosomes from two of these parents with two-copy SMN1 dosage by somatic cell hybridization and have employed a modified quantitative dosage assay to provide direct evidence that one parent is a two-copy/ zero-copy SMN1 carrier, whereas the other parent had an affected child as the result of a de novo mutation. These findings are important for assessing the recurrence risk of parents of children with spinal muscular atrophy and for providing accurate family counseling.

We utilized a heteroduplex method to screen for small mutations in Duchenne muscular dystrophy patients who did not have deletions or duplications. A dystrophin exon 53 heteroduplex band was identified in 14.4% of the affected patients. Direct sequencing of the amplified product from DNA producing the heteroduplex revealed the presence of a polymorphism in the coding region. The codon for asparagine was converted from AAT to AAC.

We describe a common dystrophin gene polymorphism in the black population that alters both HindIII and BglII restriction sites.