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Biomedical subjects

J O van Hemel

Publications and source records attributed to J O van Hemel.

At least 19 recordsLinked to original sources
PubMed1996

The fragile X phenotype in a mosaic male with a deletion showing expression of the FMR1 protein in 28% of the cells.

The instability of the CGG repeat region of FMR1 is not restricted to the CGG repeat but expands to flanking sequences as well. A mosaic fragile X male is reported with a deletion of part of the CGG repeat and 30 bp immediately 3' of the repeat, thus confirming the presence of a hotspot for deletions in the CGG region of FMR1. The deletion, detected in 28% of his lymphocytes, did not impair the transcription and translation of FMR1, suggesting that regulatory elements are not present in the deleted region. The patient has the characteristic fragile X phenotype and assuming that the mosaic pattern detected in the lymphocytes reflects the mosaic pattern in brain, 28% expression of FMRP may not be sufficient for normal cognitive functioning.

Aged↗
PubMed1996

Variable FMR1 gene methylation of large expansions leads to variable phenotype in three males from one fragile X family.

The fragile X syndrome is caused by an expanded CGG repeat (> 200 units, full mutation) at the 5' end of the FMR1 gene, which is associated with methylation of a CpG island upstream of the FMR1 gene and down regulation of the transcription. We describe three related males with full mutations in the FMR1 gene, as defined by size, but with different percentages of unmethylated alleles (+/-90%, 35%, and 15%, respectively) as studied in leucocytes. Normal mental status was observed in the male who showed 90% lack of methylation, whereas his two cousins were retarded. The mentally normal male did show some minor facial features of the fragile X syndrome; the FMR protein was detectable in 75% of his leucocytes. In all three cases, the proportion of unmethylated FMR1 genes corresponded to the percentage of leucocytes showing FMR1 protein production. Our results indicated a direct relationship between methylation and the ability to produce FMR protein. These cases will be discussed in relation to the phenotypic effects of incompletely methylated full mutations in the FMR1 gene as observed by others.

Adult↗
PubMed1995

A chromosome 21-specific cosmid cocktail for the detection of chromosome 21 aberrations in interphase nuclei.

Fluorescent in situ hybridization (FISH) with a 21q11-specific probe (CB21c1) consisting of three non-overlapping cosmids has been applied to interphase amniocytes of pregnancies at increased risk for fetal aneuploidy (N = 78) and to interphase lymphocytes, cultured and uncultured, of patients referred for Down syndrome (N = 19 and 28, respectively). In the uncultured amniocytes, six chromosome aberrations were detected: three cases of trisomy 21, a triploidy, a de novo 46,XX,t(21q21q), and a mosaic 46,XY/47,XY,+dic(21)(q11)/48,XY,+dic(21)(q11),+del(21)(q11). In 15 cultured and 20 uncultured blood samples, FISH correctly diagnosed trisomy 21 (full or mosaic) at the interphase level, which was confirmed in all cases by subsequent karyotyping. Because of specific and strong signals in interphase nuclei, CB21c1 appears to be a useful tool for the rapid detection of chromosome 21 abnormalities.

Amniocentesis↗
PubMed1994

DNA diagnosis of the fragile X syndrome in a series of 236 mentally retarded subjects and evidence for a reversal of mutation in the FMR-1 gene.

The cloning of the FMR-1 gene and the identification of an expanded CGG repeat in DNA of fragile X patients has made reliable DNA diagnosis feasible. Southern blotting and PCR assays of the CGG repeat in an unselected series of 236 mentally retarded subjects resulted in the identification of 10 new fragile X families. Reevaluation of previously assessed fragile X families resulted in the first observation of the presence of a reversal of mutation in the FMR-1 gene.

Blotting, Southern↗
PubMed1993

Clinical and molecular studies in fragile X patients with a Prader-Willi-like phenotype.

A special subphenotype of the fragile X syndrome is reported which is characterised by extreme obesity with a full, round face, small, broad hands/feet, and regional skin hyperpigmentation. It resembles the Prader-Willi syndrome (PWS) and might therefore be named 'Prader-Willi-like'. Unlike the PWS, these PW-like fragile X patients lack the neonatal hypotonia with feeding problems during infancy followed by hyperphagia from toddlerhood. We describe five new fragile X patients and present a clinical update of three previously described patients with the PW-like phenotype. In one family, segregation of either the classical Martin-Bell or the PW-like phenotype was observed and in another family there was repeated transmission of the PW-like phenotype. Previously, one of the patients had been misdiagnosed as having classical PWS, based on clinical findings. Molecular studies of the FMR-1 gene showed the typical full mutations as seen in fragile X syndrome males. Molecular analysis of the 15q11-13 region, which is deleted in the majority of classical PWS patients, did not show any detectable abnormalities. In a group of 26 patients with suspected Prader-Willi syndrome but without detectable molecular abnormalities of chromosome 15, one fragile X patient was found. These clinical and molecular findings illustrate the necessity to perform DNA analysis of the FMR-1 gene in mentally retarded patients presenting with a PW phenotype but without the PWS specific cytogenetic/molecular abnormalities of chromosome 15.

Adolescent↗
PubMed1992

Avoidance of emergency surgery in newborn infants with trisomy 18.

Trisomy 18 (Edwards' syndrome) presents with characteristic external features as well as life-threatening abnormalities; many of these abnormalities require surgical correction during the neonatal period. Children with trisomy 18 have a very short life expectancy, and all long-term survivors have severe mental retardation. Difficult medical and ethical issues arise over whether or not to institute treatment when a newborn infant with suspected trisomy 18 has a life-threatening anomaly. We studied the policy of treatment in seven patients with clinical Edwards' syndrome. For three, the period of uncertainty was shortened because trisomy 18 was rapidly diagnosed by karyotyping of a bone-marrow aspirate. Four of the patients underwent surgery before the diagnosis of trisomy 18 was confirmed by routine karyotyping in lymphocytes; karyotyping in bone marrow might have allowed invasive treatment to be avoided in three of these. Rapid confirmation of clinically suspected Edwards' syndrome is very important because surgery may then be withheld. A newborn infant with trisomy 18 should be considered as a patient with a hopeless outlook who ought not to be subjected to invasive procedures. The decision to withdraw or withhold treatment should be discussed frankly with the parents. The period of uncertainty can be reduced to a minimum by the use of karyotyping in bone marrow.

Abnormalities, Multiple↗
PubMed1992

Linkage analysis with chromosome 15q11-13 markers shows genomic imprinting in familial Angelman syndrome.

Angelman syndrome (AS) and Prader-Willi syndrome (PWS) have become the classical examples of genomic imprinting in man, as completely different phenotypes are generated by the absence of maternal (AS) or paternal (PWS) contributions to the q11-13 region of chromosome 15 as a result of deletion or uniparental disomy. Apparently, most patients are sporadic cases. The genetic mechanism underlying familial AS has remained enigmatic for a long time. Recently, evidence has been emerging suggesting autosomal dominant inheritance of a detectable or undetectable defect in a gene or genes at 15q11-13, subject to genomic imprinting. The present report describes an unusually large pedigree with segregation of AS through maternal inheritance and apparent asymptomatic transmission through several male ancestors. Deletion and paternal disomy at 15q11-13 were excluded. However, the genetic defect is still located in this region, as we obtained a maximum lod score of 5.40 for linkage to the GABA receptor locus GABRB3 and the anonymous DNA marker D15S10, which have been mapped within or adjacent to the AS critical region at 15q11-13. The size of the pedigree allowed calculation of an odds ratio in favour of genomic imprinting of 9.25 x 10(5). This family illustrates the necessity of extensive pedigree analysis when considering recurrence risks for relatives of AS patients, those without detectable deletion or disomy in particular.

Angelman Syndrome↗
PubMed1991

DNA analysis in patients with lissencephaly type I and other cortical dysplasias.

DNA markers YNZ22.1, YNH37.3, 144D6, and VAW508 were studied in five patients with the Miller-Dieker syndrome, 17 patients with the isolated lissencephaly sequence, one patient with a non-classified lissencephaly, and nine patients with an atypical cortical dysplasia. All patients had normal chromosomes except for a deletion 17p13.3 in one of the five Miller-Dieker patients. The five Miller-Dieker patients showed deletions of markers YNZ22.1 and YNH37.3 in contrast to the other patients tested. In one patient, the deletion was in the maternally contributed chromosome. Prenatal diagnosis by DNA analysis allowed exclusion of the recurrence of Miller-Dieker syndrome in a subsequent pregnancy.

Brain↗
PubMed1991

Clinical and chromosome studies of three patients with Smith-Magenis syndrome.

The authors report three patients with Smith-Magenis syndrome; only 21 patients with this syndrome have been described previously in the literature. The syndrome is related to a deletion of chromosome 17p11 x 2, and differs from Miller-Dieker syndrome on clinical criteria and in that the latter is related to a deletion of 17p13 x 3.

Adult↗
PubMed1989

[Children with autism and related contact disorders: medical aspects].

In children with infantile autism or atypical pervasive developmental disorders somatic aspects play an important role. A review is presented of important hereditary, pre-, peri- and neonatal factors, findings at neurological examination, specific medical disorders and neurochemical and neurophysiological findings. Results of the medical examination of 15 children with autistic or atypical developmental disorders are presented. It is concluded that extensive medical examination of these children is indicated: in 8 out of 15 children a clinically relevant chromosomal, neurological or biochemical disorder could be detected.

Autistic Disorder↗
PubMed1987

Sister chromatid exchanges, hyperdiploidy and chromosomal rearrangements studied in cells from melanoma-prone individuals belonging to families with the dysplastic nevus syndrome.

Cytogenetic investigations were performed on 25 individuals belonging to six melanoma-prone families with multiple melanocytic lesions (the dysplastic nevus syndrome, DNS). Patients having DNS with or without a history of melanoma were compared with clinically normal relatives and unrelated normal controls. The results indicate normal frequencies of hyperdiploidy and spontaneous sister chromatid exchanges in the fibroblasts of all individuals studied. Karyotypic analyses were carried out on the members of one family. The patients with DNS had a normal constitutional karyotype. In lymphocytes or fibroblasts from five patients, however, increased frequencies of cells with random chromosomal rearrangements were observed. These abnormalities, mainly translocations and inversions, were not found in two of the patients' spouses and in six clinically normal relatives. In the fibroblast cultures considerable clonal selection of cytogenetically abnormal cells occurred.

Chromosome Aberrations↗
PubMed1979

Partial trisomy 10q: a recognizable syndrome.

Five cases from two nonrelated families with partial trisomy 10q due to a reciprocal translocation t(10;17)(q25;p13) and t(10;11)(q24;q23), respectively, are reported. The phenotypic findings are compared with those of 17 previously published cases; the clinical data justify the conclusion that cases with trisomy 10q show a specific syndrome of mental retardation and malformation characterized by psychomotor retardation, growth retardation, hypotonia, high forehead, flat face, fine and arched eyebrows, antimongoloid slant of the eyes, narrow palpebral fissures, hypertelorism, short nose, bow-shaped mouth, short neck (kypho)scoliosis, and in some cases microcephaly.

Adolescent↗
PubMed1975

Familial occurrence of the g syndrome.

We report the familial occurrence of the G syndrome of multiple congenital anomalies affecting a mother and her three sons. All showed the characteristic syndromal facies, a low total ridge count, pronounced hypertelorism, and mild mental retardation, and severe dysphagia in infancy which improved with age but persisted in the boys (it has disappeared in the mother). One of the boys had a left cleft lip and cleft palate, another had a unilateral cleft lip. All boys had hypospadias: penile in two (with descended testes) and perineal in another (with cryptorchidism). Familial occurrence in this family is compatible with autosomal dominant inheritance.

Abnormalities, Multiple↗