In germ cells and the early embryo, the mammalian genome undergoes widespread epigenetic reprogramming. Animal studies suggest that this process is vulnerable to external factors. We report two children who were conceived by intracytoplasmic sperm injection (ICSI) and who developed Angelman syndrome. Molecular studies, including DNA methylation and microsatellite and quantitative Southern blot analysis, revealed a sporadic imprinting defect in both patients. We discuss the possibility that ICSI may interfere with the establishment of the maternal imprint in the oocyte or pre-embryo.

BackgroundClassic galactosemia is an autosomal recessive disorder due to galactose‐1‐phosphate uridyltransferase (GALT) deficiency. Newborn screening and early treatment do not completely prevent tremor, speech deficits, and diminished IQ in both sexes and premature ovarian insufficiency (POI) in women. Data on how individuals with galactosemia fare as adults will improve our ability to predict disease progression.MethodsThirty‐three adults (mean age = 32.6 ± 11.7 years; range = 18–59) with classic galactosemia, confirmed by genotype and undetectable GALT enzyme activity, were evaluated. Analyses assessed associations among age, genotype, clinical features and laboratory measures.ResultsThe sample included 17 men and 16 women. Subjects exhibited cataracts (21%), low bone density (24%), tremor (46%), ataxia (15%), dysarthria (24%), and apraxia of speech (9%). Subjects reported depression (39%) and anxiety (67%). Mean full scale IQ was 88 ± 20, (range = 55–122). All subjects followed a dairy‐free diet and 75–80% reported low intake of calcium and vitamin D. Mean height, weight and body mass were within established norms. All female subjects had been diagnosed with POI. One woman and two men had had children. Logistic regression analyses revealed no associations between age, genotype or gender with IQ, tremor, ataxia, dysarthria, apraxia of speech or anxiety. Each 10‐ year increment of age was associated with a twofold increase in odds of depression.ConclusionsTaken together, these data do not support the hypothesis that galactosemia is a progressive neurodegenerative disease. However, greater attention to depression, anxiety, and social relationships may relieve the impact of this disorder in adults.

Mutations of the human SLC26A4/PDS gene constitute the most common cause of syndromic and nonsyndromic hearing loss. Definition of the SLC26A4 mutation spectrum among different populations with sensorineural hearing loss is important for development of optimal genetic screening services for congenital hearing impairment. We screened for SLC26A4 mutations among Chinese and U.S. subjects with hearing loss, using denaturing HPLC (DHPLC) and direct DNA sequencing. Fifty-two of 55 Chinese subjects with deafness accompanied by enlargement of the vestibular aqueduct (EVA) exhibited at least one mutant SLC26A4 allele, whereas SLC26A4 mutations were found in only 2 of 116 deaf Chinese patients without EVA. The spectrum of SLC26A4 mutations differed among Chinese and U.S. subjects and included 10 previously unreported SLC26A4 variants: 4 in the Chinese population (p.E303Q, p.X329, p.X467, p.X573) and 6 in the U.S. population (p.V250A, p.D266N, p.F354S, p.D697A, p.K715N, p.E737D). Among the seven novel in-frame missense mutations, five encoded SLC26A4 proteins with substantially reduced Cl(-)/anion exchange activity as expressed and measured in Xenopus oocytes, but four of these were sufficiently active to allow study of anion selectivity. The only mutant polypeptide exhibiting complete loss of anion exchange function, p.E303Q, was expressed at or near the oocyte surface at near-wild-type levels. Two variants, p.F354S and p.E737D, displayed selective reduction in relative rate of Cl(-)/HCO(3)(-) exchange compared with similarly measured rates of Cl(-)/Cl(-) and Cl(-)/I(-) exchange. Our data show that mutation analysis of the SLC26A4 gene is of high diagnostic yield among subjects with deafness and bilateral EVA in both China and the U.S. However, the pathogenicity of monoallelic SLC26A4 gene variants in patients with hearing loss remains unclear in many instances.

Purpose: Hearing loss is a common congenital disorder that is frequently associated with mutations in the GJB2 gene encoding the connexin 26 protein (Cx26). We sought to evaluate the effectiveness of direct DNA sequencing for detection of Cx26 mutations as a clinical diagnostic test. Methods: We designed a clinical assay using a three-step polymerase chain reaction (PCR)-based DNA sequencing strategy to detect all possible mutations in the open reading frame and flanking sequences of Cx26. The results of the first 324 cases of childhood deafness referred for diagnostic testing were analyzed. Results: A total of 127 of the 324 (39.2%) cases had at least one mutant Cx26 allele (36.1% of sporadic cases, 70% of familial cases). Of these 127 case, 57 (44.8%) were homozygotes or compound heterozygotes. Thirty-four different mutations were identified, including 10 novel mutations, 6 of which (T8M, K15T, R32L, M93I, N206S, and 511-512insAACG) may be pathogenic. We also provide new evidence on the pathogenicity or nonpathogenicity of 12 previously reported mutations, and clarify the confusing nomenclature of the 313-326del14 mutation. Key Words: connexin 26 (GJB2), Cx26 mutation, congenital hearing loss, deafness, molecular diagnosticsHearing loss is a common congenital disorder, affecting 0.1% to 0.2% of all newborns. Of these cases,~60% are inherited and~80% of inherited deafness falls under the category of autosomal recessive, nonsyndromic hearing loss. 1-3 Within this category,~50% of severe to profound cases are classified as DFNB1 in the ethnic populations tested 4,5 and are caused by mutations in the GJB2 gene, 6 -9 which encodes the protein connexin 26 (Cx26), a member of the connexin family of proteins. These proteins are major constituents of intercellular gap junctions, and Cx26 is believed to play a crucial role in regulating potassium ion flux during auditory transduction in the inner ear. 10 -12 In addition, a few autosomal dominant deafnesscausing mutations in Cx26 have also been described, classified clinically as DFNA3. 5 Moreover, mutations in Cx26 (and in other connexins) have been associated with syndromic deafness, including Vohwinkel syndrome, palmoplantar keratoderma, and erythrokeratodermas. [13][14][15][16][17] Several studies have demonstrated a wide spectrum of Cx26 mutations associated with hearing loss in patients with a broad range of deafness. Although the most common mutation is 35delG, the prevalences and carrier frequencies of the different mutations vary among peoples of different ethnicities. 18 -32 Over 70 pathogenic recessive or dominant mutations, and close to 20 allelic variants with undetermined pathogenicity or polymorphisms, have been reported. [33][34][35] However, no clear genotype-phenotype correlations have been established. 36 -41 We report here the results of a sequence-based mutation analysis of the connexin 26 (GJB2) gene in blood samples from 324 children (and appropriate family members) sent for clinical molecular diagnostic testing for familial or sporadic deafn...