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EN
Deafness is a complex disorder that is affected by a high number of genes and environmental factors. Recently, enormous progress has been made in nonsyndromic deafness research, with the identification of 90 loci and 33 nuclear and 2 mitochondrial genes involved (http://dnalab-www.uia.ac.be/dnalab/hhh/). Mutations in the GJB3 gene, encoding the gap junction protein connexin 31 (Cx31), have been pathogenically linked to erythrokeratodermia variabilis and nonsyndromic autosomal recessive or dominant hereditary hearing impairment. To determine the contribution of the GJB3 gene to sporadic deafness, we analysed the GJB3 gene in 67 families with nonsyndromic hearing impairment. A single coding exon of the GJB3 gene was amplified from genomic DNA and then sequenced. Here we report on three amino acid changes: Y177D (c.529T > G), 49delK (c.1227C > T), and R32W (c.144-146delGAA). The latter substitution has been previously described, but its involvement in hearing impairment remains uncertain. We hypothesize that mutations in the GJB3 gene are an infrequent cause of nonsyndromic deafness.
EN
Familial adenomatous polyposis (FAP) is a well-known hereditary condition characterised by alimentary system tumours. Tens to thousands of polyps occur in the colon and rectum of the patients. There is a high heterogeneity with regard to the number and time of the occurrence of polyps. The occurrence of FAP is associated with mutations in the APC tumour suppressor gene, which was described in 1991. Since then, many studies have been done to analyse the distribution of mutations in individual populations and to determine the function of the gene and a diagnostic approach to FAP. Here the APC gene was studied with respect to the occurrence of small mutations and large rearrangements in 300 unrelated Polish FAP families. Ninety-seven mutations were identified in 164 families. Out of these mutations, 80 were small mutations, including 58 small mutations that were first identified in the Polish population (42 novel and 16 described previously). An increased frequency of mutation c.3927_3931delAAAGA was observed in 10% of the Polish group. Seventeen large rearrangements were found in 29 families. Out of those rearrangements, 8 repeat rearrangements occurred in 20 families. A problem in fast molecular diagnostics of FAP is a high heterogeneity of mutations in the APC gene. It seems that a multiplex ligation-dependent probe amplification test and searching for small mutations by the use of screening methods at the 5' end of exon 15 and exons 14, 9, 11, 13, 5, and 3, help to improve the molecular diagnostics of FAP in Polish patients.
EN
The glomerular filtration barrier consists of endothelial cells, the glomerular basement membrane, and podocytes. The membrane is a highly crosslinked macromolecular meshwork composed of specific extracellular matrix proteins. The adjacent foot processes of podocytes are bridged along their basolateral surfaces by a slit diaphragm (a porous filter structure of nephrin molecules). Recent discoveries of mutations in the range of genes encoding proteins involved in the structure or function of the glomerular filtration barrier have provided new insights into mechanisms of glomerular diseases. In this review, we summarize recent progress in the elucidation of the genetic basis of some glomerulopathies in humans.
EN
The SRY gene (sex-determining region on the Y chromosome; MIM *480000) is responsible for initiating male gonadal development. However, only 15?20% of the cases of XY gonadal dysgenesis are due to mutations in its sequence. Recently, heterozygous mutations in the NR5A1 gene (nuclear receptor subfamily 5, group A, member 1; MIM +184757) have been described in association with ovarian failure and disorders of testis development with or without adrenal failure. Here we describe a case of XY complete gonadal dysgenesis due to a p.D293N homozygous mutation in the NR5A1 gene, with normal SRY and no adrenal failure.
EN
Natural history of the disease in 4 unrelated Polish children with homozygous familial hypercholesterolemia (FH) is described. Their phenotypic homozygosity was established by identification of known LDLR gene mutations on both alleles, respectively: p.G592E & p.G592E in Patient 1; p.G592E & p.C667Y in Patient 2; p.S177L & p.R350X in Patient 3; and p.G592E & deletion in the promoter region, exons 1 and 2 in Patient 4. Heterozygosity of the mutations was revealed in all patients' mothers and fathers (obligatory heterozygotes) and in 1 out of 4 siblings studied. FH was diagnosed at the age of 4 months to 9 years by cholesterol screening among family members of patients with early cardiovascular disease episodes. At the time of FH detection, the children were asymptomatic. Only in 2, some skin eruptions were found. Antihyperlipidemic therapy was started, including a lipid-lowering diet, cholestyramine, and HMG-CoA inhibitors if necessary. No cardiovascular symptoms appeared during the observation up to the age of 18, 20, 19, and 17 years, respectively. An increase in external carotid artery diameter was found in a patient at the age of 9 years, and LDL-apheresis was introduced in his therapy. We conclude that the analysis of LDLR gene mutations in the studied FH children made it possible to identify 4 presymptomatic FH homozygotes and to introduce early appropriate treatment. Multicenter analysis of such persons would finally determine if the early lipid-lowering procedures can significantly reduce the risk of premature cardiovascular disease in homozygous FH.
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