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M Genuardi

Publications and source records attributed to M Genuardi.

At least 55 records · Page 3Linked to original sources
PubMed1996

Fragile X founder chromosomes in Italy: a few initial events and possible explanation for their heterogeneity.

A total of 137 fragile X and 235 control chromosomes from various regions of Italy were haplotyped by analyzing two neighbouring marker microsatellites, FRAXAC1 and DXS548. The number of CGG repeats at the 5' end of the FMR1 gene was also assessed in 141 control chromosomes and correlated with their haplotypes. Significant linkage disequilibrium between some "major" haplotypes and fragile X was observed, while other "minor" haplotypes may have originated by subsequent mutation at the marker microsatellite loci and/or recombination between them. Recent evidence suggests that the initial mechanism leading to CGG instability might consist of rare (10 (-6/-7)) CGG repeat slippage events and/or loss of a stabilizing AGG via A-to-C transversion. Also, the apparently high variety of fragile X chromosomes may be partly due to the relatively high mutation rate (10 (-4/-5)) of the microsatellite markers used in haplotyping. Our fragile X sample also showed a higher than expected heterozygosity when compared to the control sample and we suggest that this might be explained by the chance occurrence of the few founding events on different chromosomes, irrespective of their actual frequency in the population. Alternatively, a local mechanism could enhance the microsatellite mutation rate only on fragile X chromosomes, or fragile X mutations might occur more frequently on certain background haplotypes.

Alleles↗
PubMed1996

Extended gene diversity at the FMR1 locus and neighbouring CA repeats in a sub-Saharan population.

We report on the allele distributions in a normal black African population at two microsatellite loci neighbouring the FRAXA locus and at the CGG repeat in the 5' end of the FMR-1 gene, which causes the fragile X syndrome. The CGG repeat distribution was found to be similar to that of other ethnic groups, as well as to that of other nonhuman primates, possibly predicting a comparable prevalence of fragile X in Africa. Significant linkage disequilibrium has been observed between fragile X mutations and alleles of the DXS548 and FRAXAC1 loci in European and Asian populations, and some founder chromosomes may be extremely old. Those associated with FRAXAC1-A and DXS548-2 alleles are not present in the Asian fragile X samples. We searched for these alleles and their frequency in the well defined Bamileke population of Cameroon. All previously described alleles and some new ones were found in this sample, supporting the hypothesis of their pre-existence and subsequent loss in Asian populations. Finally, the heterozygosity of the Bamileke sample was significantly higher at both marker loci and comparable to that of Europeans at the CGG repeat, confirming the notion that genetic diversity is greater in Africans than in other groups and supporting the view that evolution of modern man started in Africa.

Africa South of the Sahara↗
PubMed1996

Hereditary nonpolyposis colorectal cancer: review of clinical, molecular genetics, and counseling aspects.

Lynch syndrome, or hereditary nonpolyposis colon cancer (HNPCC), is an autosomal-dominant disease accounting for approximately 1-5% of all colorectal cancer cases. Due to the lack of pathognomonic morphological or biomolecular markers, HNPCC has traditionally posed unique problems to clinicians and geneticists alike, both in terms of diagnosis and clinical management. Recently, novel insight into the pathogenesis of this syndrome has been provided by the identification of its molecular basis. In HNPCC families, germline mutations in any of four genes encoding proteins of a specialized DNA repair system, the mismatch repair, predispose to cancer development. Mutations in mismatch repair genes lead to an overall increase of the mutation rate and are associated with a phenotype of length instability of microsatellite loci. The present report summarizes the clinicopathological aspects of HNPCC and reviews the most recent molecular and biochemical findings.

Colorectal Neoplasms, Hereditary Nonpolyposis↗
PubMed1996

A split hand-split foot (SHFM3) gene is located at 10q24-->25.

The split hand-split foot (SHSF) malformation affects the central rays of the upper and lower limbs. It presents either as an isolated defect or in association with other skeletal or non-skeletal abnormalities. An autosomal SHSF locus (SHFM1) was previously mapped to 7q22.1. We report the mapping of a second autosomal SHSF locus to 10q24-->25. A panel of families was tested with 17 marker loci mapped to the 10q24-->25 region. Maximum lod scores of 3.73, 4.33 and 4.33 at a recombination fraction of zero were obtained for the loci D10S198, PAX2 and D10S1239, respectively. An 19 cM critical region could be defined by haplotype analysis and several genes with a potential role in limb morphogenesis are located in this region. Heterogeneity testing indicates the existence of at least one additional autosomal SHSF locus.

Abnormalities, Multiple↗
PubMed1996

Telomerase activity in human laryngeal squamous cell carcinomas.

The activation of telomerase has been shown to be an important step during tumorigenesis in a variety of malignancies and is associated with characteristics of cellular immortality, such as indefinite proliferative potential. We studied telomerase activity in a series of human laryngeal carcinomas. Thirty-six tumors from 35 patients were studied using a sensitive PCR-based technique, the telomeric repeat amplification protocol assay. Telomerase activity was present in 32 tumors (89%), and the level of activity correlated with the stage of disease. In two of four telomerase-negative tumors, we found evidence of an inhibitor of telomerase activity. In many cases, samples of mucosa surrounding the tumor were also studied, and telomerase could be detected in 16 of 21 patients. For this reason, we proceeded to perform a topographical analysis that demonstrated a pattern of telomerase activity suggestive of a spread of telomerase-positive cells. In conclusion, these data indicate that telomerase activation is important for laryngeal carcinogenesis and that telomerase assay might be a valuable addition to determine the spread of the disease.

Carcinoma, Squamous Cell↗
PubMed1995

Proximal femoral focal deficiency (PFFD) and fibular A/hypoplasia (FA/H): a model of a developmental field defect.

Proximal femoral focal deficiency (PFFD) and fibular a/hypoplasia (FAH) are distinct malformations of the lower limbs. Both can occur as isolated defects or in association with other limb malformations. In fact, fibular defects frequently are present in PFFD, and, conversely, femoral abnormalities can be found in the presence of a typical FAH picture. We report on 5 patients with a variable combination of femoral and fibular defects. In one of them unilateral PFFD was associated with lateral foot defects, in the absence of fibular abnormalities, and with a phenotype similar to that observed in the femoral hypoplasia/unusual face syndrome (FH/UFS). Another patient had isolated PFFD on one side, with controlateral absence of femur, fibula, and tibia. Another patient had a PFFD, fibular hypoplasia, and abnormalities of fibular foot rays, and the last 2 patients, a father and son, had, respectively, bilateral foot malformations plus fibular and tibial hypoplasia in the father and a PFFD in the son. These observations represent a further demonstration of the existence of a fibular developmental field, and contribute to the definition of its spatial boundaries. The variable involvement of elements comprised in the developmental field can be explained by multifactorial etiology.

Abnormalities, Multiple↗
PubMed1995

Ulnar ray defect in an infant with a 6q21;7q31.2 translocation: further evidence for the existence of a limb defect gene in 6q21.

Ectrodactyly is a developmental defect of the distal limbs characterized by marked clinical variability and genetic heterogeneity, also reflected in the observation of different chromosome abnormalities non randomly associated with longitudinal postaxial limb deficiencies. The one most frequently found in patients with split hand-split foot (SHSF) involves chromosome band 7q22. Recently, structural anomalies of chromosome 6q21 have been reported in 2 unrelated patients with SHSF, suggesting that this region may also contain genes responsible for limb development [Braverman et al., 1993. Am J Hum Genet, suppl 53: 410; Viljoen and Smart, 1993. Clin Dysmorph 2: 274-277]. We report on a third patient who had a de novo, apparently balanced t(6;7)(q21;q31.2) translocation and bilateral ulnar aplasia with postaxial oligodactyly. In spite of the different phenotypic effects observed in these 3 patients, we consider our case as further evidence that genes in 6q21 may play a role in distal limb development.

Chromosome Banding↗
PubMed1995

First report of t(8;21)(q22;q22) in a case of de novo acute monoblastic leukemia.

Here we describe the case of a 30-year-old man with a diagnosis of de novo acute monoblastic leukemia (FAB M5a), whose karyotype analysis revealed the presence of the translocation (8;21)(q22;q22) as the sole chromosome anomaly. In spite of the rather good prognosis patients suffering from acute leukemia and carrying this translocation are supposed to have, our patient had a very poor outcome, including an early relapse resistant to any treatment and meningeal localization. Death occurred within 5 months from diagnosis. To our knowledge this is the first report of t(8;21)(q22;q22) in de novo acute monoblastic leukemia.

Adult↗
PubMed1995

Dicentric chromosome Y associated with Leydig cell agenesis and sex reversal.

The nature of a non-mosaic marker Y chromosome observed in a pseudohermaphrodite patient with Leydig cell agenesis was investigated by high-resolution chromosome analysis and molecular probes from the Y chromosome. Cytogenetically, the marker chromosome appeared to be an isodicentric, with breakage in Yq11.21. Double copies of all Yp-specific loci tested, including SRY, were present. The most distal Yq portion detected in patient DNA was DXS278-C, which maps to interval D in the chromosome Yq deletion map. Fragment DXS278-B, which maps to deletion interval E, was absent. The possible relationship between this cytogenetic abnormality and Leydig cell agenesis, a finding never reported in association with Y chromosome rearrangements, is discussed.

Adolescent↗
PubMed1994

Split hand/split foot, syndactyly, urinary tract obstruction, radial, diaphragmatic, and neural tube defects: Czeizel-Losonci syndrome?

We report on a baby girl with absence of the left hemidiaphragm, lumbosacral myelomeningocele, syndactyly with limb deficiencies, and bilateral hydronephrosis. A similar array of malformations was described previously by Czeizel and Losonci [Hum Genet 77:203-204, 1987] in a single family which showed a transmission pattern suggesting autosomal dominant inheritance with variable expressivity. The presence of limb abnormalities and the location of the neural tube defects in these cases suggest that the underlying pathogenesis probably does not involve the same disturbances of midline field development which have been postulated to occur in the schisis association.

Abnormalities, Multiple↗
PubMed1994

Gene for Simpson-Golabi-Behmel syndrome is linked to HPRT in Xq26 in two European families.

Linkage analysis was performed in 2 previously described European families segregating for the Simpson-Golabi-Behmel (SGB) syndrome. In both kindreds close linkage without recombination (zmax = 4.45 at theta = 0.00) was observed between the disease locus and the HPRT locus mapped in Xq26. These data are very similar to those (zmax = 7.5 at theta = 0.00) reported recently by others after studying a large Dutch-Canadian kindred with SGB syndrome. Compiled lod scores from the 3 families reach their maximum of 11.95 at recombination fraction of 0.00 with one lod unit support interval of 0.00-0.04.

Abnormalities, Multiple↗
PubMed1994

Polymorphisms of the prion protein gene in Italian patients with Creutzfeldt-Jakob disease.

Creutzfeldt-Jakob disease (CJD) is a transmissible neurodegenerative disorder characterized by the accumulation of the amyloid protein PrP in the CNS. Two coding polymorphisms of the PrP gene (PRNP) are a methionine (Met) to valine (Val) change at codon 129, and a deletion in the octapeptide coding region. In the United Kingdom, homozygosity at codon 129 appears to be associated with a predisposition to develop CJD. However, in Japan, where allelic frequencies and genotype distribution are significantly different, such an association has not been demonstrated. To determine whether such deletion(s) or codon 129 polymorphisms of PRNP predispose to the development of CJD in Italian patients, 31 sporadic CJD patients with no known PRNP mutations, and 186 unrelated control subjects were studied. Genotypic frequencies at codon 129 in these Italian CJD patients revealed a significant excess of methionine alleles, and a different genotype distribution in comparison with the normal Italian population. Deletions of a 24-bp segment located in the PrP octapeptide coding region were found in two control subjects, but in none of the sporadic CJD patients. These data suggest that Met homozygosity at codon 129 may contribute, with other environmental or endogenous factors, to CJD development.

Adult↗
PubMed1994

A new case of interstitial deletion of chromosome 3q, del(3q)(q13.12q21.3), with agenesis of the corpus callosum.

We describe a boy with an interstitial deletion of the proximal portion of chromosome 3q. Prominent physical characteristics were a dysmorphic face with apparent hypertelorism, signs of prenatal lymphedema, foot contractures and agenesis of the corpus callosum. The finding of corpus callosum agenesis in a previously reported patient with an overlapping deletion suggests an additional locus for this malformation.

Abnormalities, Multiple↗