Jacques Poncin

Mutation analysis of the MEN1 gene in Belgian patients with multiple endocrine neoplasia type 1 and related diseases

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized by tumors in parathyroids, enteropancreatic endocrine tissues, anterior pituitary, and other tissues. The gene for MEN1 has recently been cloned and shown to code for a 610‐amino acid protein of enigmatic function which probably acts as a tumor suppressor. Several mutations causing the MEN1 phenotype have been recently identified. In order to determine the spectrum of MEN1 gene mutations in a sample of 25 Belgian patients, we have systematically screened the 10 exons and adjacent sequences of the MEN1 gene by means of an automatic sequencing protocol. Twelve different mutations were identified including nonsense, frameshift, splicing, and missense mutations. Two of these mutations (D172Y and 357del4) occurred more than once. A missense mutation was also found in a kindred with familial hyperparathyroidism. We observed no significant correlation between the nature or position of mutation and the clinical status. We have also detected 6 intragenic polymorphisms and DNA sequence variants and have analyzed their frequencies in our population. Hum Mutat 13:54–60, 1999.

Paternal Uniparental Disomy for Chromosome 1 Revealed by Molecular Analysis of a Patient with Pycnodysostosis

Molecular analysis of a patient affected by the autosomal recessive skeletal dysplasia, pycnodysostosis (cathepsin K deficiency; MIM 265800), revealed homozygosity for a novel missense mutation (A277V). Since the A277V mutation was carried by the patients father but not by his mother, who had two normal cathepsin K alleles, paternal uniparental disomy was suspected. Karyotyping of the patient and of both parents was normal, and high-resolution cytogenetic analyses of chromosome 1, to which cathepsin K is mapped, revealed no abnormalities. Evaluation of polymorphic DNA markers spanning chromosome 1 demonstrated that the patient had inherited two paternal chromosome 1 homologues, whereas alleles for markers from other chromosomes were inherited in a Mendelian fashion. The patient was homoallelic for informative markers mapping near the chromosome 1 centromere, but he was heteroallelic for markers near both telomeres, establishing that the paternal uniparental disomy with partial isodisomy was caused by a meiosis II nondisjunction event. Phenotypically, the patient had normal birth height and weight, had normal psychomotor development at age 7 years, and had only the usual features of pycnodysostosis. This patient represents the first case of paternal uniparental disomy of chromosome 1 and provides conclusive evidence that paternally derived genes on human chromosome 1 are not imprinted.

A novel gene overexpressed in the prostate of castrated rats: hormonal regulation, relationship to apoptosis and to acquired prostatic cell androgen independence.

We have identified a novel complementary DNA (cDNA) corresponding to a gene overexpressed in the rat ventral prostate after castration. This cDNA displays 89.4% identity with 453 bp of a mouse EST and 81.5% identity with 157 bp of a human EST and was named PARM-1 for prostatic androgen-repressed message-1. The complete cDNA is 1187 bp long and codes for a protein of 298 amino acids that contains four potential glycosylation sites and three half cystinyl residues. The PARM-1 gene was found to be expressed at quite low levels in most rat tissues including those of the urogenital tract. The kinetic of induction of PARM-1 gene in the prostate was highly correlated to the development of apoptosis in the whole organ. Supplementation of castrated animals with androgens reversed both the process of apoptosis and the overexpression of PARM-1 gene. Supplementation with estrogens did not result in an increase in the PARM-1 messenger RNA levels when compared with the castration alone. However, the treatment resulted ...

APC mutations in human colorectal adenomas: analysis of the mutation cluster region with temperature gradient gel electrophoresis and clinicopathological features.

To date, the earliest mutations in colorectal adenomas have been found in the adenomatous polyposis coli (APC) gene, considered the ‘gatekeeper’ in tumourigenesis. To study the types of APC gene mutations and their relation to clinicopathological features which are associated with malignant potential, the mutation cluster region of the APC gene was analysed in a series of 32 human sporadic colorectal adenomas from 22 patients. DNA was extracted from frozen sections and two overlapping fragments which cover the mutation cluster region were amplified using the polymerase chain reaction (PCR). Mutations were screened with temperature gradient gel electrophoresis and identified by DNA sequencing. Mutations were found in 14 samples (44 per cent) from 11 patients. The changes could be characterized as point mutations (n=7), deletions of one or more nucleotides (n=6), and insertions (n=1). From five patients, multiple adenoma samples were obtained and the adenomas from two of these patients showed a heterogeneous mutation pattern in the APC gene. All detected mutations are predicted to result in a truncated APC protein. Genetic alterations in the mutation cluster region of the APC gene occurred significantly more frequently in large adenomas and showed a trend towards an increase in villous adenomas and adenomas with moderate and severe dysplasia. It is concluded that an increased proportion of APC gene mutations were found in the adenomas showing clinicopathological features associated with increased proliferation but not with characteristics of malignant potential. The results suggest that in a significant proportion of adenomas, other (genetic) alterations are involved in early tumourigenesis.