Search

Investigating novel genetic variants involved in intellectual disability (ID) development is essential. X-linked intellectual disability (XLID) accounts for over 10% of all cases of ID in males. XLID genes are involved in many cellular pathways and processes. Some of them are not specific to the development and functioning of the neural system. The implementation of exome sequencing simplifies the search for novel variants, especially those less expected. Here, we describe a nonsense variant of the XLID gene, WDR13 . The mutation c.757C>T (p.Arg253Ter) was uncovered by X-chromosome exome sequencing in males with a familial form of intellectual disability. Quantitative PCR (qPCR) analysis showed that variant c.757C>T caused a significant decrease in WDR13 expression in the patient's fibroblast. Moreover, it dysregulated other genes linked to intellectual disability, such as FMR1 , SYN1 , CAMK2A , and THOC2 . The obtained results indicate the pathogenic nature of the detected variant and suggest that the WDR13 gene interacts with other genes essential for the functioning of the nervous system, especially the synaptic plasticity process.

Hailey-Hailey disease (HHD) is a rare, late-onset autosomal dominant genodermatosis characterized by blisters, vesicular lesions, crusted erosions, and erythematous scaly plaques predominantly in intertriginous regions. HHD is caused by ATP2C1 mutations. About 180 distinct mutations have been identified so far; however, data of only few cases from Central Europe are available. The aim was to analyze the ATP2C1 gene in a cohort of Polish HHD patients. A group of 18 patients was enrolled in the study based on specific clinical symptoms. Mutations were detected using Sanger or next generation sequencing. In silico analysis was performed by prediction algorisms and dynamic structural modeling. In two cases, mRNA analysis was performed to confirm aberrant splicing. We detected 13 different mutations, including 8 novel, 2 recurrent (p.Gly850Ter and c.325-3 T > G), and 6 sporadic (c.423-1G > T, c.899 + 1G > A, p.Leu539Pro, p.Thr808TyrfsTer16, p.Gln855Arg and a complex allele: c.[1610C > G;1741 + 3A > G]). In silico analysis shows that all novel missense variants are pathogenic or likely pathogenic. We confirmed pathogenic status for two novel variants c.325-3 T > G and c.[1610C > G;1741 + 3A > G] by mRNA analysis. Our results broaden the knowledge about genetic heterogeneity in Central European patients with ATP2C1 mutations and also give further evidence that careful and multifactorial evaluation of variant pathogenicity status is essential.

Diverse subcellular localizations of the huntingtin-containing inclusion bodies are frequently suspected of reflecting crucial divisions between different cellular pathways contributing to the pathophysiology of Huntington's disease. Here, we use a panel of different N-terminal huntingtin fragments overexpressed in transfected neuronal and non-neuronal cells to demonstrate that it is the length of the N-terminal huntingtin fragments rather than a presence of any specific amino acid sequences that determines the ratio between the nuclear and cytoplasmic inclusion bodies. Importantly, the length of those fragments does also seem to strongly influence the folding of the aggregating huntingtin species, as indicated by the apparent differences in their accessibility for different antibodies directed against particular subdomains within the N-terminal part of huntingtin, although these differences do not correlate with the peptides' ability to efficiently aggregate within the cell nucleus. Furthermore, the relatively long huntingtin fragment containing 588 amino acids of the reference sequence shows intracellular behavior that is substantially different from that exhibited by its shorter counterparts (containing either 171, 120, 89 or 64 amino acids), as this rarely aggregating peptide is not only accumulating in cytoplasmic inclusions of slightly different morphology but is also most strongly affected by the FLAG-tagging procedure that unexpectedly induces (or enhances) autophagy-related processes. Together, our results reveal a significant heterogeneity of the huntingtin accumulation patterns that are observed at the cellular level. These patterns are not only strongly dependent on both the length and the amino acid composition of the N-terminal huntingtin peptides but also seem to engage different cellular mechanisms implicated in the pathogenesis of Huntington's disease, including the non-proteasomal degradation of potentially toxic huntingtin forms., (Copyright © 2015 Elsevier GmbH. All rights reserved.)

Unlabelled: The Pelizaeus-Merzbacher disease (PMD) is a rare X-linked recessive hypomyelination disorder caused by mutations of the proteolipid protein1 gene (PLP1). There is a spectrum of PLP1-related disorders from very severe connatal PMD, through classical PMD to mild spastic paraplegia type 2 (SPG2), with some correlation between the type of mutation and the phenotype. In general, missense mutations give rise to more severe forms of the disease, deletions and null mutations to mild PMD and SPG2. The most common variations, duplications, result in the classical-intermediate form of PMD., The Aim: To report the analysis of mutations in the PLP1 gene and phenotype di!erences in ten male patients diagnosed with PMD. Although they had different types of PLP1 mutations (duplications, missense and nonsense mutations), all of them were clinically classi"ed with the classical form of PMD (clPMD)., Material and Methods: The subjects of analysis were ten male patients aged 1.5 to 21 years who were diagnosed with PMD. All patients developed the "rst clinical symptoms between 1 an 8 months of age and showed developmental delay, mainly in motor skills. All were classified with the classical form of the disease, according to international clinical criteria and the electrophysiological and brain MRI criteria of hypomyelination. The molecular analysis of the PLP1 gene involved dosage analysis and direct sequencing of all exons and promotor region of the gene., Results: The clinical diagnosis of PMD was con"rmed for all subjects by molecular analysis of the PLP1gene. Although all had the classical form of PMD, it was caused by mutations of di!erent types: duplications of the entire gene, missense and nonsense mutations., Conclusions: Our clinical and molecular "ndings showed that the phenotypic spectrum resulting from PLP1 mutations seems to be broader in patients with the PLP1 gene duplication compared to patients with both nonsense and missense mutation. Nevertheless, apart from the type of mutation, all our patients’ clinical manifestation falls into the category of the classical form of PMD according to international criteria. Obviously the type of mutations, but also other unidentified factors may a!ect the clinical course of PMD.The Pelizaeus-Merzbacher disease (PMD) is a rare X-linked recessive hypomyelination disorder caused by mutations of the proteolipid protein 1 gene (PLP1). There is a spectrum of PLP1-related disorders from very severe connatal PMD, through classical PMD to mild spastic paraplegia type 2 (SPG2), with some correlation between the type of mutation and the phenotype. In general, missense mutations give rise to more severe forms of the disease, deletions and null mutations to mild PMD and SPG2. The most common variations, duplications, result in the classical-intermediate form of PMD., The Aim: To report the analysis of mutations in the PLP1 gene and phenotype differences in ten male patients diagnosed with PMD. Although they had di!erent types of PLP1 mutations (duplications, missense and nonsense mutations), all of them were clinically classi"ed with the classical form of PMD (clPMD)., Material and Methods: The subjects of analysis were ten male patients aged 1.5 to 21 years who were diagnosed with PMD. All patients developed the "rst clinical symptoms between 1 an 8 months of age and showed developmental delay, mainly in motor skills. All were classified with the classical form of the disease, according to international clinical criteria and the electrophysiological and brain MRI criteria of hypomyelination. The molecular analysis of the PLP1 gene involved dosage analysis and direct sequencing of all exons and promotor region of the gene., Results: The clinical diagnosis of PMD was con"rmed for all subjects by molecular analysis of the PLP1 gene. Although all had the classical form of PMD, it was caused by mutations of di!erent types: duplications of the entire gene, missense and nonsense mutations., Conclusions: Our clinical and molecular findings showed that the phenotypic spectrum resulting from PLP1 mutations seems to be broader in patients with the PLP1 gene duplication compared to patients with both nonsense and missense mutation. Nevertheless, apart from the type of mutation, all our patients' clinical manifestation falls into the category of the classical form of PMD according to international criteria. Obviously the type of mutations, but also other unidentified factors may a!ect the clinical course of PMD.

Background and Purpose: Parkinson disease (PD) is a complex disease, comprising genetic and environmental factors. Despite the vast majority of sporadic cases, three genes, i.e. PARK2, PINK1 and PARK7 (DJ-1), have been identified as responsible for the autosomal recessive form of early-onset Parkinson disease (EO-PD). Identified changes of these genes are homozygous or compound heterozygous mutations. The frequency of PARK2, PINK1 and PARK7 mutations is still under debate, as is the significance and pathogenicity of the single heterozygous mutations/variants, which are also detected among PD patients. The aim of the study was to analyze the incidence of autosomal recessive genes PARK2, PINK1, PARK7 mutations in Polish EO-PD patients., Material and Methods: The analysis of the PARK2, PINK1 and PARK7 genes was performed in a group of 150 Polish EO-PD patients (age of onset < 45 years). Mutation analysis was based on sequencing and gene dosage abnormality identification., Results: Mutations were identified only in the PARK2 and PINK1 genes with the frequency of 4.7% and 2.7% of subjects, respectively. In PARK2, point mutations and exons' rearrangements, and in PINK1 only missense mutations were detected. In both genes mutations were found as compound heterozygous/homozygous and single heterozygous. EO-PD patients' genotype-phenotype correlation revealed similarities of clinical features in mutation carriers and non-carriers., Conclusions: The frequency of the PARK2, PINK1, PARK7 mutations among Polish EO-PD patients seems to be low. The role of single heterozygous mutations remains a matter of debate and needs further investigations.

Dystrophic Epidermolysis Bullosa (DEB) is a genetic disease caused by mutations in the COL7A1 gene that is inherited in the autosomal dominant or recessive mode. We have developed a curated, freely accessible COL7A1 specific database (http://www.col7.info), which contains more than 730 reported and unpublished sequence variants of the gene. Molecular defects are reported according to HGVS recommendation. The clinical description module is provided with an advanced search tool together with a CSV (comm. separated values) data format download option. This compilation of COL7A1 data and nomenclature is aimed at assisting molecular and clinical geneticists to enhance the collaboration between researchers worldwide., (© 2011 Wiley Periodicals, Inc.)

Dystrophic Epidermolysis Bullosa (DEB) is a rare bullous genodermatosis caused by mutations in COL7A1, which encodes collagen type VII, the main component of anchoring fibrilis. DEB is inherited in an autosomal recessive and dominant manner, depending on the mutation type and localization. The aim of this study was to update the spectrum and frequency of COL7A1 mutations in a cohort of 42 Polish DEB patients. Using direct sequencing strategy we identified 25 different mutations, which gave us a detection rate of about 88%. In total, thirteen novel variants were identified, including three de novo mutations (p.G2680S, p.G2043R and p.Gly2064&#95;Arg2069del). The panel of recessively inherited DEB causing recurrent mutations comprise of five variants: c.425A>G, c.682+1G>A, p.R2069C, p.W796X and, unreported before, c.7154delC, which accounts for about 59% of all mutated alleles in this group. In the dominant type of DEB, only p.G2043R was found to be recurrent and it was identified in 50% patients. Our results give further insight into the pathogenesis and epidemiology of DEB.

Objective: Mutations in the PARK2 (Parkin) gene result in an early-onset autosomal recessive form of Parkinson Disease (EO-PD). Although the frequency of the PARK2 mutations in EO-PD patients according to several studies is high and has been reported in up to 50% in familial and 19% in sporadic cases, these data remain controversial., Methods: We performed PARK2 gene analysis for a group of 79 Polish EO-PD patients with onset of disease below the age of 40. All exons were directly sequenced and the exons' copy number variations were analyzed., Results: Mutations in PARK2 gene were found in 3 patients (3.8%), in two sporadic cases in both alleles (2.5%) and in a familial case in only one allele (1.3%). We identified point mutations as well as exon rearrangements (duplication, deletion)., Conclusions: The frequency of the PARK2 mutations our Polish group with EO-PD seems to be lower than in other previously described groups., (Copyright 2009 Elsevier Ltd. All rights reserved.)

Unlabelled: Mental retardation affects 2-3% of the population. The identification of nonspecific X-linked mental retardation genes represents a challenge of considerable medical and scientific importance., Aim: An attempt to identify new genes and mutations in known genes in 14 families with nonspecific X-linked mental retardation., Material and Methods: Linkage analysis with microsatellite markers was performed in 14 families with mental retardation segregating as an X-linked feature. Significant lod score (> 2) was obtained only for 2 families, due to insufficient number of analyzed families' members. Known MRX genes located in the linkage intervals were analysed., Results: Analysis of selected known MRX genes enabled identification of pathogenic mutations in 3 out of 14 families. Sequencing of further candidate genes is in progress. In all families the critical region and the number of genes to analyze was significantly narrowed., Conclusions: Linkage analysis in families with mental retardation segregating as an X-linked feature is still a considerable approach leading to identification of new genes, and mutations in known genes. It is a first step of identification of disease background, even in small families with lod score < 2.

Hereditary hearing loss (HL) is a very heterogeneous trait, with 46 gene identifications for non-syndromic HL. Mutations in GJB2 cause up to half of all cases of severe-to-profound congenital autosomal recessive non-syndromic HL, with 35delG being the most frequent mutation in Caucasians. Although a genotype-phenotype correlation has been established for most GJB2 genotypes, the HL of 35delG homozygous patients is mild to profound. We hypothesise that this phenotypic variability is at least partly caused by the influence of modifier genes. By performing a whole-genome association (WGA) study on 35delG homozygotes, we sought to identify modifier genes. The association study was performed by comparing the genotypes of mild/moderate cases and profound cases. The first analysis included a pooling-based WGA study of a first set of 255 samples by using both the Illumina 550K and Affymetrix 500K chips. This analysis resulted in a ranking of all analysed single-nucleotide polymorphisms (SNPs) according to their P-values. The top 250 most significantly associated SNPs were genotyped individually in the same sample set. All 192 SNPs that still had significant P-values were genotyped in a second independent set of 297 samples for replication. The significant P-values were replicated in nine SNPs, with combined P-values between 3 x 10(-3) and 1 x 10(-4). This study suggests that the phenotypic variability in 35delG homozygous patients cannot be explained by the effect of one major modifier gene. Significantly associated SNPs may reflect a small modifying effect on the phenotype. Increasing the power of the study will be of greatest importance to confirm these results.

Mental retardation (MR) affects approximately 2% of the population. About 10% of all MR cases result from defects of X-linked genes. Mutations in most of more than 20 known genes causing nonspecific form of X-linked MR (MRX) are very rare and may account for less than 0.5-1% of MR. Linkage studies in extended pedigrees followed by mutational analysis of known MRX genes in the linked interval are often the only way to identify a genetic cause of the disorder. We performed linkage analysis in several MRX families, and in one family with four males with MR we mapped the disease to an interval encompassing Xp21.2-22.11 (with a maximum LOD score of 2.71). Subsequent mutation analysis of genes located in this interval allowed us to identify a partial deletion of the IL1RAPL1 gene. Different nonoverlapping deletions involving IL1RAPL1 have been reported previously, suggesting that this region could be deletion-prone. In this report, we present the results of the molecular analyses and clinical examinations of four affected family members with the deletion in IL1RAPL1. Our data further confirm the importance and usefulness of linkage studies for gene mapping in MRX families and demonstrate that IL1RAPL1 plays an important role in the etiology of MRX. With the development of new methods (aCGH, MLPA), further rearrangements in this gene (including deletions and duplications) might be discovered in the nearest future., (Copyright (c) 2008 Wiley-Liss, Inc.)

Objectives: Defects of PRSS1, SPINK1, CFTR and AAT are considered causative or predisposing to pancreatitis. The aim of this study was to evaluate the impact of these defects into molecular pathology of chronic pancreatitis (CP) and acute recurrent pancreatitis (ARP)., Methods: Ninety-two children with CP or ARP, 55 family members and 50 controls were investigated. The subjects were screened for PRSS1 mutations: R122H, R122C, A16V, N29I; SPINK1 N34S variant; panel of 14 CFTR defects: INNOLiPA CFTR12, CFTRdele2,3 and IVS8-T variant or panel of 3 CFTR defects-F508del, CFTRdele2,3 and IVS8-T; AAT mutations: E264V, E342K., Results: We identified 1 mutated allele in at least 1 of 4 genes in 31 of 92 patients and 12 of 50 controls (P = 0.157). Mutations in SPINK1 and PRSS1 were most frequent. PRSS1 mutations were identified mainly in CP patients (9.6% of CP vs 2.5% of ARP alleles, P = 0.094), whereas N34S SPINK1 mutation was present with comparable frequency in CP and ARP patients (7.7% vs 10.0%, P = 0.768). The frequency of mutations in CFTR alleles was similar to controls (4.9% vs 5%, P = 0.587). Overall frequency of AAT mutations was lower than in the controls. Family studies showed that defects in the examined genes did not always segregate with disease., Conclusions: PRSS1 defects seem to be causative for pancreatitis, whereas defects in SPINK1 are suggested to be associated with the disease. No association between CFTR mutations and pancreatitis was observed. The importance of AAT variants remains speculative.

Hearing impairment (HI) affects 1 in 650 newborns, which makes it the most common congenital sensory impairment. Despite extraordinary genetic heterogeneity, mutations in one gene, GJB2, which encodes the connexin 26 protein and is involved in inner ear homeostasis, are found in up to 50% of patients with autosomal recessive nonsyndromic hearing loss. Because of the high frequency of GJB2 mutations, mutation analysis of this gene is widely available as a diagnostic test. In this study, we assessed the association between genotype and degree of hearing loss in persons with HI and biallelic GJB2 mutations. We performed cross-sectional analyses of GJB2 genotype and audiometric data from 1,531 persons, from 16 different countries, with autosomal recessive, mild-to-profound nonsyndromic HI. The median age of all participants was 8 years; 90% of persons were within the age range of 0-26 years. Of the 83 different mutations identified, 47 were classified as nontruncating, and 36 as truncating. A total of 153 different genotypes were found, of which 56 were homozygous truncating (T/T), 30 were homozygous nontruncating (NT/NT), and 67 were compound heterozygous truncating/nontruncating (T/NT). The degree of HI associated with biallelic truncating mutations was significantly more severe than the HI associated with biallelic nontruncating mutations (P<.0001). The HI of 48 different genotypes was less severe than that of 35delG homozygotes. Several common mutations (M34T, V37I, and L90P) were associated with mild-to-moderate HI (median 25-40 dB). Two genotypes--35delG/R143W (median 105 dB) and 35delG/dela(GJB6-D13S1830) (median 108 dB)--had significantly more-severe HI than that of 35delG homozygotes.

Introduction: Chronic granulomatous disease (CGD)is a rare inherited disorder in which phagocytic cells are unable to generate superoxide anions. Patients with CGD are predisposed to recurrent bacterial and fungal infections because the superoxide-generating NADPH oxidase activity is needed for efficient killing of microbes. Among the at least 5 subunits cre-ating a functional NADPH oxidase, a molecular defect located in any of the gp91phox, p22phox, p47phox, or p67phox subunits may cause CGD., Material/methods: In this study,8 patients were diagnosed with CGD on the basis of clinical findings and absence of nitroblue tetrazolium reduction in phagocytes. Southern blot analysis, GeneScan, and direct sequencing were performed to define particular DNA mutations., Results: Among 6 X-linked CGD (X-CGD)patients, 4 different mutations were identified in the X-linked CYBB gene (encoding gp91phox)by direct sequencing. A novel missense mutation, located in the NADPH-binding region of gp91phox,was found in 2 brothers. One frameshift 1578delA, one splicing 252G->A mutation, and one partial gene deletion were also identified. The molecular defect in the NCF1 gene (encoding p47phox)was established in 2 patients. One was DeltaGT/DeltaGT homozygote, the other carried, besides this GT deletion on one allele, a unique Phe118stop mutation on the other., Conclusions: In general, the X-CGD patients within the group followed a more severe clinical course than the patients with an NCF1 defect. However, the lack of a straightforward genotype phenotype correlation indicates that the clinical severity of CGD depends also on other antimicrobial host-defense systems.

An abbreviated tract of five thymidines (5T) in intron 8 of the cystic fibrosis transmembrane conductance regulator (CFTR) gene is found in approximately 10% of individuals in the general population. When found in trans with a severe CFTR mutation, 5T can result in male infertility, nonclassic cystic fibrosis, or a normal phenotype. To test whether the number of TG repeats adjacent to 5T influences disease penetrance, we determined TG repeat number in 98 patients with male infertility due to congenital absence of the vas deferens, 9 patients with nonclassic CF, and 27 unaffected individuals (fertile men). Each of the individuals in this study had a severe CFTR mutation on one CFTR gene and 5T on the other. Of the unaffected individuals, 78% (21 of 27) had 5T adjacent to 11 TG repeats, compared with 9% (10 of 107) of affected individuals. Conversely, 91% (97 of 107) of affected individuals had 12 or 13 TG repeats, versus only 22% (6 of 27) of unaffected individuals (P<.00001). Those individuals with 5T adjacent to either 12 or 13 TG repeats were substantially more likely to exhibit an abnormal phenotype than those with 5T adjacent to 11 TG repeats (odds ratio 34.0, 95% CI 11.1-103.7, P<.00001). Thus, determination of TG repeat number will allow for more accurate prediction of benign versus pathogenic 5T alleles.

The GJB2 gene defects are the most frequent cause of autosomal recessive non-syndromic hearing loss (DFNB1). Epidemiological data suggest that 35delG is the most prevalent mutation found in 88% of mutated alleles. Another mutations - 313del14 was found in 7% of mutated alleles. The other mutations were identified only in single families. Following the analysis of distribution of GJB2 mutations in the Polish population we propose an algorithm for molecular diagnosis of DFNB1. We propose to screen all patients affected with prelingual non-syndromic deafness for 35delG mutation using ASO or multiplex AS-PCR methods. The presence of 35delG on two alleles confirms DFNB1. The identification of heterozygous 35delG mutation requires additional GJB2 analysis including 313del14 mutation detection and en exon 2 direct sequencing. To determinate the frequency of digenic (GJB2/GJB6) background of DFNB we screened 17 patients with heterozygous 35delG mutation for deletion of 342 kb in GJB6 gene. No such mutation was detected in the analyzed group.

The A1555G mutation in the 12SrRNA gene has been associated with aminoglycoside induced and nonsyndromic sensorineural hearing impairment. In this study we analyzed Hungarian, Polish and German patients with nonsyndromic severe to profound hearing impairment of unknown origin for this mutation. The frequency of the A1555G mutation in the Hungarian hearing impaired population was below 1.8 %. Three out of 125 Polish patients carrying the A1555G mutation were identified. Among German patients one carrier was found (0.7 %) revealing a homoplastic A1555G mutation, whereas no mutation was detected in control individuals with normal hearing (frequency < 0.6%). In summary the frequencies of the A1555G mutation are low in the hearing impaired as well as in the normal population in Hungary, Poland and Germany. Since the importance of this mutation and its relationship with aminoglycoside exposure is not well understood yet, patients with nonsyndromic hearing impairment should be routinely screened for this mutation to avoid aminoglycoside induced hearing impairment due to increased sensitivity of maternal relatives., (Copyright 2002 Wiley-Liss, Inc.)

We report an analysis of 102 unrelated Polish patients with profound prelingual deafness for mutations in the GJB2 gene (OMIM #220290). Mutations were found in 41/102 (40%) subjects. Among mutated alleles, 35delG was prevalent and present in 88%. In nine alleles, different mutations were found: M34T, Q47X, R184P, and 313del14 (found in 6 patients). The results prove mutations in the GJB2 gene are responsible for much hereditary nonsyndromic deafness in Poland, with a strong prevalence of the 35delG mutation. We have also found a high carrier frequency (1/50) for the 35delG mutation in the Polish population.

Hereditary hyperphenylalaninemia (HPA) is a disorder of amino acid metabolism and results from an insufficiency of hepatic phenylalanine hydroxylase (PAH). HPA phenotypes form a spectrum ranging from classical phenylketonuria (PKU) to mild hyperphenylalaninemia (MHP). The phenotypic diversity reflects heterogeneity at the molecular level, and more than 320 different mutations in the PAH gene are known to date. The association of 3 mutations (R408W, IVS10 and A403V) common in different European populations with a variable number tandem repeat (VNTR) and short tandem repeat sites (minihaplotype) in the PAH gene was examined in a group of Polish PKU and MHP patients. Additionally, minihaplotypes were established for another 16 mutations. The presented data support the hypothesis that the R408W/VNTR3/STR238 allele originated among pre-Indo-Europeans on the territory in present-day Lithuania and Belarus. Mutation IVS10nt-11g-->a (IVS10) is strongly associated with VNTR7/STR250 minihaplotype and is possibly of Mediterranean origin., (Copyright 2000 S. Karger AG, Basel.)

Polish CF patients were screened extensively for mutations in the CFTR gene. Screening data demonstrated a high heterogeneity of CFTR mutations in the Polish population. Total 30 different mutations were characterised in 24 exons or introns of the gene. Among them, six mutations have been reported for the first time and submitted to the CF Genetic Analysis Consortium. In addition, 15 different polymorphisms were found, including three new ones. The screening resulted in 9% increase of the detection rate of CFTR alleles in the tested population. Frequencies of two of the identified mutations (CFTRdele2,3 and 2184insA) are relatively high (2.6% and 1%, respectively) and justify their inclusion into routinely screened mutations in genetic testing of Polish CF population.

Obstructive azoospermia is one of the symptoms of congenital bilateral absence of the vas deferens (CBAVD)--disease which is suggested as primarily genital form of cystic fibrosis. CBAVD is a result of mutations and polymorphisms in CFTR gene. We studied 9 the most common mutations and identified 3 mutations (delta F508, R117H, G542X). The study showed that: 37.1% of CBAVD patients (13 out of 35 examined patients) carried mutations in a single or both copies of the gene. We also found the increased frequency of IVS8-5T allele in this group. No increased frequency of mutations in CFTR gene was found in group of men with incorrect spermatogenesis.

Based on the Polish Registry of Cystic Fibrosis the analysis of alive CF adults (18 y.a. and more) was performed. Out of 156 Polish CF adults, in 106 (68.0%) identification of the CFTR gene mutations was performed. Relative frequencies of 24 mutations of CFTR gene mutations is 72.2%. Frequencies of the most common mutations are: delta F508 49.06%, 3849 + 10kbCT 8.96%, G542X 1.89%; in Polish CF adults mutations other than delta F508 comprise 23.13% of CF alleles. The most common genotype delta F508/delta F508 occurs with the frequency 22.6%, significantly lower than in CF children; genotype delta F508/3849 + 10kbCT occurs with the frequency 11.3%, and this value is significantly higher than in other age groups.

Mutations in the genes encoding different parts of phenylalanine hydroxylation system cause persistent hyperphenylalaninaemia. The most frequent form of hyperphenylalaninaemia is caused by mutations in the PAH gene. The most common variant result from defect of tetrahydrobiopterin synthase. Mutations in the PAH and PTS genes in the Polish population are presented. Genotype--phenotype correlations are discussed.

N1303K is one of the most frequent non-delta F508 mutations causing cystic fibrosis in Central Europe. Since no restriction site is altered by this mutation and no other frequent mutations are known so far in exon 21, the detection requires a separate and laborious test. A mismatched primer was used to create an artificial Hin dIII site in amplified wildtype DNA, which is destroyed by the mutation. This allows for rapid and convenient detection by restriction enzyme digestion.

A cystic fibrosis patient homozygous for the nonsense mutation R553X was identified by mutation screening and the genotype confirmed by DNA sequencing. This patient, the only one described to date who is homozygous for this stop codon in exon 11 of the CFTR gene, is moderately severely affected. Clinical and molecular findings are presented.

A total of 75 non-delta F508 chromosomes from 59 German cystic fibrosis patients was screened for mutations in exon 11 of the cystic fibrosis (CFTR) gene. These Caucasian patients were found to possess an identical haplotype background for two common mutations (G551D, R553X) consistent with their being identical by descent. However, a different R553X associated haplotype found in American black patients was suggestive of recurrent mutation, a postulate supported by the location of the R553X alteration in a hypermutable CpG dinucleotide. Likelihood estimates for recurrent mutation and identity by descent were compared and strongly supported the hypothesis of recurrent R553X mutation. The ability to distinguish between these two alternatives provides an indication of whether or not the search for mutations should be restricted to chromosomes with similar haplotypes.