The frequency of GJB2 and GJB6 mutations in the New York State newborn population: feasibility of genetic screening for hearing defects.

In the US, approximately one in every 1000 children has hearing loss sufficiently severe to interfere with the acquisition of normal speech [Ann NY Acad Sci 630 (1991) 16]. The causes of non-syndromic hearing loss (NSHL) are known to be heterogeneous, with genetic factors accounting for 50-75%[Am J Med Genet 46 (1993) 486]. Often individuals with NSHL thought to be caused by mutations in GJB2 have only one detectable mutant allele [Am J Hum Genet 62 (1998) 792, Hum Mol Genet 6 (12) (1997) 2173]. Another gene that has been identified as a possible cause of NSHL is GJB6 that codes for the gap junction protein, connexin 30. A consecutive series of anonymous newborn dried blood specimens (n = 2089) was tested for two GJB2 mutations: (i) 35delG, a pan-ethnic mutation; and (ii) 167delT, a mutation more frequently found in individuals of Ashkenazi Jewish and Mediterranean descents. Mutation detection was validated using allele-specific oligonucleotide hybridization in single wells. Once the positive samples had been identified, the samples were pooled and retested. All positives in the individual experiment were correctly identified in the pooled experiment. The same random set of anonymous newborn dried blood specimens plus some additional samples were tested (n = 2112) for the 342-kb deletion in the GJB6 gene.

Population-based studies reveal differences in the allelic frequencies of two functionally significant human interleukin-4 receptor polymorphisms in several ethnic groups.

PURPOSE: The presence of functionally significant human interleukin-4 receptor sequence variants, Gln551Arg and Ile50Val, was examined in four anonymous New York State populations defined by ethnic origin. These variants were studied because they are associated with atopy or atopic asthma whose prevalence varies in different populations. METHODS: PCR/RFLP (Ile50Val) and PCR/allele-specific oligonucleotide hybridization (Gln551Arg) assays were developed to detect both polymorphisms in 855 newborn screening specimens. RESULTS: Arg551 was most frequently found in Blacks (allele frequency of 68%). However, the Ile50 allele was most common in Whites (allele frequency, 87%). Significantly more Blacks had chromosomes bearing both of the "enhanced signaling" variants (Ile50/Arg551). CONCLUSIONS: Enhanced IL-4R signaling is associated with increased IgE production (atopy). Therefore, our data suggest that the African American population may be at increased risk for diseases, including asthma, which are associated with atopy. These data also emphasize the importance of determining the frequencies of single nucleotide polymorphisms in different populations before drawing conclusions from allele association studies, since the background allele frequencies may be disparate between different populations.

Blood spot screening and confirmatory tests for syphilis antibody.

We developed a blood spot test for syphilis antibody using enzyme-linked immunosorbent assay (ELISA) technology. Dried blood was eluted by buffered saline or, for a supplementary confirmatory test, by treponemal-antibody test diluent. Eluates were diluted in an absorption buffer (Calypte Biomedical, Berkeley, Calif.) and added to plate wells coated with cardiolipin antigen (ADI Diagnostics, Toronto, Ontario, Canada). The wells were washed and treated sequentially with an immunoglobulin G conjugate, buffer washes, and enzyme substrate. Substrate conversion was measured photometrically, and specimen reactivity was determined by reference to nonreactive controls. The optimum test protocol was established by tests of serum and plasma. The serum ELISA specificity with normal specimens was 98.9%. The sensitivity with sera from patients with undefined syphilis was 97.4%, that with sera from patients with documented primary and secondary disease was 100%, and that with sera from patients with early and late latent disease was 95.7%. The specificity of the spot test with donor blood was 94.2%, and its specificity with newborn blood was 94.9%. The sensitivity with 25 spots spiked with reactive sera was 96%. The seroprevalence rates for parturient women in one hospital were 6.01% according to spot tests of sera from 599 newborns and 6.81% according to Rapid Plasma Reagin tests of 499 maternal serum specimens. Seventy percent of infants born to 50 seropositive women were reactive by either the newborn spot or the Rapid Plasma Reagin serum test. The results show that blood spots may be used in seroprevalence or serodiagnostic studies, especially to identify women who are infected or to identify possible cases of congenital infection. The test provides for studies of children and adults when routine venipuncture and serum handling and storage are problematic.