Extensive scanning of the calpain-3 gene broadens the spectrum of LGMD2A phenotypes.

BACKGROUND: The limb girdle muscular dystrophies (LGMD) are a heterogeneous group of Mendelian disorders highlighted by weakness of the pelvic and shoulder girdle muscles. Seventeen autosomal loci have been so far identified and genetic tests are mandatory to distinguish among the forms. Mutations at the calpain 3 locus (CAPN3) cause LGMD type 2A. OBJECTIVE: To obtain unbiased information on the consequences of CAPN3 mutations. PATIENTS: 530 subjects with different grades of symptoms and 300 controls. METHODS: High throughput denaturing HPLC analysis of DNA pools. RESULTS: 141 LGMD2A cases were identified, carrying 82 different CAPN3 mutations (45 novel), along with 18 novel polymorphisms/variants. Females had a more favourable course than males. In 94% of the more severely affected patient group, the defect was also discovered in the second allele. This proves the sensitivity of the approach. CAPN3 mutations were found in 35.1% of classical LGMD phenotypes. Mutations were also found in 18.4% of atypical patients and in 12.6% of subjects with high serum creatine kinase levels. CONCLUSIONS: A non-invasive and cost-effective strategy, based on the high throughput denaturing HPLC analysis of DNA pools, was used to obtain unbiased information on the consequences of CAPN3 mutations in the largest genetic study ever undertaken. This broadens the spectrum of LGMD2A phenotypes and sets the carrier frequency at 1:103.

Clinical variability and molecular diagnosis in a four-generation family with X-linked Emery-Dreifuss muscular dystrophy.

AIM: To describe the clinical variability of X-linked Emery-Dreifuss muscular dystrophy (X-EDMD) with cardiac involvement in a four-generation family with a novel mutation in the STA gene. METHODS: Clinical data were provided for 4 affected males and a female carrier. The Western blot analysis of emerin was performed on lymphoblastoid cell lines and followed by sequencing of the emerin gene. RESULTS: A thymine insertion at nucleotide 417 in exon 2, resulting in a frameshift with a premature stop codon at position 62 and absence of functional protein, was found in one of the three available patients. In ten-year-old proband's dizygotic twin-nephews the intermittent first-degree A-V block, atrial and ventricular ectopy, atrial runs, and exit sinus block were found, although the echocardiographic findings were normal. One of the twins also had short episodes of atrial fibrillation, idioventricular rhythm, and junctional rhythm. CONCLUSION: Cardiac abnormalities in the proband's ten-year-old dizygotic twins without evident clinical features suggestive of EDMD were remarkable in contrast to the oldest patient in the family, who lived to the age of 63 without a pacemaker, and to the proband who had a very early onset of muscle wasting and weakness, and a pacemaker implantation at the age of 27. This striking intra-familial variability in cardiac involvement associated with specific null mutation (417 ins T) has practical early diagnostic and possibly preventive implications. It also points at genetic and environmental factors as causes of clinical features in X-EDMD.

A cluster of cystic fibrosis mutations in exon 17b of the CFTR gene: a site for rare mutations.

Intensive screening has improved our understanding of the profile of mutations in the CFTR gene in which more than 400 mutations have been detected to date. In collaboration with several European laboratories we are involved in such analysis. We have identified 14 new mutations in exon 17b of CFTR, having analysed 780 CF chromosomes, and have compared the frequency of mutations in this exon with that of other regions of the CFTR gene. The results obtained indicate an accumulation of mutations, not only in regions encoding the two nucleotide binding folds, but also in those encoding transmembrane domains of the CFTR gene, in particular exon 17b.

Identification of three novel mutations (457 TAT-->G, D192G, Q685X) in the Slovenian CF patients.

Chromosomes from a cohort of 60 Slovenian families, corresponding to the 121 cystic fibrosis (CF) chromosomes available, were fully scanned for mutations in the coding sequence of the cystic fibrosis transmembrane conductance regulator (CFTR) gene (The 60 families yielded 121 CF alleles because the mother of one patient was also affected). This corresponds to the 27 exons and intron/exon boundaries that have been studied in chromosomes carrying unidentified alleles. As a result of this survey 84% of the alleles are now clearly identified and we describe in this paper three novel mutations (457 TAT-->G, D192G, and Q685X).

MTCP-1: a novel gene on the human chromosome Xq28 translocated to the T cell receptor alpha/delta locus in mature T cell proliferations.

T-cell lymphoproliferative diseases are often associated with recurrent chromosomal translocations involving T cell receptor genes (TCR) and genes that are thought to play a role in the pathogenesis of these diseases. Whereas numerous such genes have already been identified in acute T cell leukemias, no candidate gene has yet been identified to play a role in the heterogeneous group of T cell proliferations with a mature phenotype. We here report the molecular cloning of two examples of the rare but recurrent t(X;14) translocation. The first translocation was associated with a benign clonal proliferation in an ataxia telangiectasia patient and the second with a T cell prolymphocytic leukemia. Both translocations implicated the TCR alpha/delta locus and a common breakpoint region on chromosome Xq28. A previously unidentified gene, abnormally transcribed in both T cell proliferations, was characterized in the immediate proximity of the breakpoints. This Xq28 gene has no homology with known sequences, uses a complex alternative splicing pattern and demonstrates two short open reading frames. This gene, named MTCP-1 (Mature T Cell Proliferation-1) is the first candidate gene potentially involved in the leukemogenic process of mature T cell proliferations.

Prevalence of retinitis pigmentosa in Slovenia.

Two hundred and twenty-nine symptomatic patients with retinitis pigmentosa were ascertained in Slovenia between 1986 and 1990. Twenty-three further patients were identified while data from 63 families (82 patients) were being collected. After correction for underascertainment, a prevalence of 1 in 6023 was estimated in the Slovene population (1,999,477 in 1990). The highest prevalence of 1 in 1902 was found in the age group 65 years and older. Of 63 analysed families, 17 (27%) showed autosomal dominant, 13 (21%) autosomal recessive, and one family (1.5%) X-linked inheritance; in 30 families (47.5%) isolated cases were found; and in two families the mode of inheritance was impossible to determine.

Cystic fibrosis gene mutations and linked RFLPs in the Slovenian population.

The authors used polymerase chain reaction to analyse 56 Slovenian cystic fibrosis (CF) chromosomes for the presence of delta F508 and eight other most frequent mutations located in exons 7,11 and 20 (R347P, R334W, G551D, R553X, S549RA, S549RT, S549I and S1255X) of the CF gene. We also determined the frequency of haplotypes associated with CF for six linked RFLP markers (MetD/TaqI, MetH/TaqI, XV-2c/TaqI, KM-19/PstI, MP6d9/MspI and J3.11/MspI) in 27 Slovenian CF families. delta F508 mutation was present in 55.4 percent of the CF chromosomes. No case of the other mutations were detected in the sample of tested CF chromosomes. A very high degree of association (0.88) has been found between DNA marker MetH and CF (as measured by the Yule's association coefficient) in our population. Using the RFLP markers XV-2c and KM-19, we found that 85% of delta F508 mutated chromosomes have a single 1 2 (B) haplotype, and that this haplotype is present on only 15.4 percent of CF chromosomes without this deletion.

Lethal short limb dwarfism with dysmorphic face, omphalocele and severe ossification defect: Piepkorn syndrome or severe "boomerang dysplasia"?

The authors report a case of lethal neonatal dwarfism characterized by striking micromelia, fused rudimentary and supernumerary digits, large, soft head, pronounced hypertelorism, protruding eyes set laterally, enormous omphalocele and severe deficiency of tubular bone and spine ossification. Histologic examination showed lack of ossification of the cartilaginous anlage of many tubular bones. The cartilage had irregularly distributed chondrocytes. The matrix contained hypocellular and degenerated areas with scattered large chondrocytes. In a few bones a very disorganized growth cartilage was present. The case is similar to that described by Piepkorn et al. (1977) and may represent a severe form of "boomerang dysplasia" (Kozlowski et al., 1981; Tenconi et al., 1983; Kozlowski et al., 1985; Winship et al., 1990).

Pseudodiastrophic dysplasia evolution with age and management. Report of two new cases and review of the literature.

Two new patients with pseudodiastrophic dysplasia are reported. Clinical and radiologic features, genetics, as well as, course and management of the disease are described for these two patients and seven others reported in the literature. Based also on histological findings, special emphasis is put on differential diagnosis with diastrophic dysplasia.