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Biomedical subjects

M Le Merrer

Publications and source records attributed to M Le Merrer.

At least 73 records · Page 4Linked to original sources
PubMed1998

Novel recurrent nonsense mutation causing neurofibromatosis type 1 (NF1) in a family segregating both NF1 and Noonan syndrome.

Neurofibromatosis type 1 (NF1), a genetic disorder with neuroectodermal involvement, demonstrates phenotypic overlap in some patients with Noonan syndrome (NS), ultimately resulting in the so-called neurofibromatosis-Noonan syndrome (NF-NS). A strong association of the two phenotypic traits was recently illustrated by a four-generation family, although NF1 and NS were eventually demonstrated to segregate independently on the basis of polymorphic DNA markers [Bahuau et al., 1996: Am J Med Genet 66:347-355]. Identification of the causal NF1 mutation seemed a prerequisite to further dissecting this singular familial association. Using the protein truncation assay, a nonsense mutation (C2446T-->R816X) of the neurofibromin gene was evidenced. This mutation occurred on a CpG dinucleotide within exon 16 and 5' to the GAP domain-specifying region of the gene. R816X creates a recognition site for endonuclease HphI, absent in 2 individuals with NS only. Screening 184 unrelated NF1 patients, three novel occurrences of the mutation were found in individuals diagnosed with classical NF1. Based on the assumption of genotype-phenotype correlation in these individuals, clinical and molecular analyses of this four-generation family demonstrated that the NF-NS phenotype was additive, being the result of both classical NF1 and NS. This particular observation also suggests the presence of an NS locus on 17q, which might be of interest for further linkage studies.

DNA Mutational Analysis↗
PubMed1998

Syndromal and nonsyndromal primary trigonocephaly: analysis of a series of 237 patients.

From a series of 1,713 patients with craniosynostosis hospitalized between 1976 and 1996, 237 propositi with metopic synostosis were analyzed. The prevalence of metopic synostosis was estimated in the order of 1 in 15,000 children. Family information was obtained from 184 propositi from 179 families. The male-to-female ratio was 3.3:1. There was no maternal or paternal age effect. A family history was obtained in 10 of the 179 families, giving a 5.6% figure of familial cases. The frequency of twinning was 7.8% with two concordances for metopic synostosis in two monozygotic twin pairs. The male-to-female ratio, the twinning frequency, and the proportion of familial cases in trigonocephaly are very similar to those observed in scaphocephaly, which also involves the longitudinal sutural system. Fetal exposure to valproic acid was noticed in eight cases. The series was divided into two groups: nonsyndromal trigonocephaly (n = 184) and trigonocephaly associated with other malformations (n = 53). The second group included 13 cases of well-delineated syndromes and 40 cases of trigonocephaly associated with one or more malformations, but without any known syndrome, that could be undelineated syndromes. These groups differed significantly in their mental prognosis.

Birth Weight↗
PubMed1998

Metaphyseal anadysplasia type II: a new regressive metaphyseal dysplasia.

We report on six unrelated children, three boys and three girls, with a metaphyseal dysplasia of early onset and spontaneous regressing evolution. During the first months of life the children present with enlargement of costochondral junctions and knobby wrists. On radiographs the metaphyseal changes of the knees are specific with fine irregularities. The femoral necks are blurred but not hypoplastic. The stature is not affected and there are no metabolic abnormalities. The radiographic findings regress during growth and the abnormalities disappear after the age of ten years. These metaphyseal changes and their mode of inheritance are different from previous cases described as anadysplasia. We propose therefore to delineate this syndrome as a new type of regressive metaphyseal dysplasia and to name it anadysplasia type II.

Cartilage↗
PubMed1998

Presentation of six cases of Stüve-Wiedemann syndrome.

Stüve-Wiedemann syndrome (SWS) is a rare disorder characterized by bowing of the long bones, camptodactyly, respiratory distress, hyperthermic episodes and early lethality. We report six additional cases of SWS, suggesting that this syndrome is homogeneous. All patients had feeding and swallowing difficulties, respiratory insufficiency, dysmorphic features and radiolucent metaphyses with abnormal trabecular pattern. Recurrent episodes of unexplained fever was the cause of death in almost all cases. Parental consanguinity and recurrence in sibs is highly suggestive of autosomal recessive inheritance.

Abnormalities, Multiple↗
PubMed1998

Spatio-temporal expression of FGFR 1, 2 and 3 genes during human embryo-fetal ossification.

Mutations in FGFR 1-3 genes account for various human craniosynostosis syndromes, while dwarfism syndromes have been ascribed exclusively to FGFR 3 mutations. However, the exact role of FGFR 1-3 genes in human skeletal development is not understood. Here we describe the expression pattern of FGFR 1-3 genes during human embryonic and fetal endochondral and membranous ossification. In the limb bud, FGFR 1 and FGFR 2 are initially expressed in the mesenchyme and in epidermal cells, respectively, but FGFR 3 is undetectable. At later stages, FGFR 2 appears as the first marker of prechondrogenic condensations. In the growing long bones, FGFR 1 and FGFR 2 transcripts are restricted to the perichondrium and periosteum, while FGFR 3 is mainly expressed in mature chondrocytes of the cartilage growth plate. Marked FGFR 2 expression is also observed in the periarticular cartilage. Finally, membranous ossification of the skull vault is characterized by co-expression of the FGFR 1-3 genes in preosteoblasts and osteoblasts. In summary, the simultaneous expression of FGFR 1-3 genes in cranial sutures might explain their involvement in craniosynostosis syndromes, whereas the specific expression of FGFR 3 in chondrocytes does correlate with the involvement of FGFR 3 mutations in inherited defective growth of human long bones.

Bone and Bones↗
PubMed1998

[Trigonocephaly: isolated, associated and syndromic forms. Genetic study in a series of 278 patients].

UNLABELLED: From a series of 1,833 patients with craniosynostosis, 278 cases with metopic synostosis were analysed. The prevalence of metopic synostosis was estimated in the region of 1 in 15,000 children. PATIENTS AND METHODS: All patients with metopic suture fusion were selected, excluding cases where additional sutures were involved. The age at diagnosis was between 15 days and 15 years. The diagnosis was based on clinical and radiological evaluation. The search for associated malformations was based on clinical evaluation, CT or MRI scans, bone X-rays and ultrasounds. If possible, a study of the karyotype was performed in case of associated malformation. Family information was obtained through contact with the families, generally in person or sometimes by telephone. The series was divided into three groups: isolated trigonocephaly (group 1), trigonocephaly associated with other malformations without any known syndrome (group 2) and well delineated syndromes (group 3). RESULTS: There were 213 males and 65 females, a sex ratio of 3.3. Family information was obtained from 222 probands distributed among 216 families. There was no maternal or paternal age effect. The frequency of twinning was 7.9%, with three concordances for metopic synostosis in three monozygotic twin pairs. A positive family history was obtained in 13 of the 216 pedigrees, giving a 6% figure of familial cases. A vertical transmission was observed in only one case; in all other cases, there were two affected children with normal parents. Eleven familial cases were isolated trigonocephalies, and two were syndromic. Nine of the 53 available karyotypes were abnormal, involving the chromosomes 7, 9, 11 or 13. There were 208 observations in the group 1. In 53 cases (group 2), associated malformations involved mainly the heart (12 cases), the limbs (six cases), the brain (five cases) and the genito-urinary tract (four cases). These malformations were unique in 32 cases and multiple in 21 cases. Some: of the observations could represent new syndromes. Seventeen syndromes represented group 3. Nine were chromosomal syndromes. Eleven presented with multiple malformations. An in utero exposure to valproic acid was observed in two cases of the group 1, five cases of the group 2 and one case of the group 3.

Abnormalities, Multiple↗
PubMed1998

SHOX mutations in dyschondrosteosis (Leri-Weill syndrome).

Dyschondrosteosis (DCS) is an autosomal dominant form of mesomelic dysplasia with deformity of the forearm (Madelung deformity; ref. 3). Based on the observation of XY translocations (p22,q12; refs 4-6) in DCS patients, we tested the pseudoautosomal region in eight families with DCS and showed linkage of the DCS gene to a microsatellite DNA marker at the DXYS233 locus (Zmax=6.26 at theta=0). The short stature homeobox-containing gene (SHOX), involved in idiopathic growth retardation and possibly Turner short stature, maps to this region and was therefore regarded as a strong candidate gene in DCS. Here, we report large-scale deletions (in seven families) and a nonsense mutation (in one family) of SHOX in patients with DCS and show that Langer mesomelic dwarfism results from homozygous mutations at the DCS locus.

Female↗
PubMed1998

A gene for Meckel syndrome maps to chromosome 11q13.

Meckel syndrome (MKS) is a rare autosomal recessive lethal condition of unknown origin, characterized by (i) an occipital meningo-encephalocele with (ii) enlarged kidneys, with multicystic dysplasia and fibrotic changes in the portal area of the liver and with ductal proliferation, and (iii) postaxial polydactyly. A gene responsible for MKS in Finland has been mapped to chromosome 17q21-q24. Studying a subset of Middle Eastern and northern African MKS families, we have recently excluded the chromosome 17 region and have suggested a genetic heterogeneity. In the present study, we report on the mapping of a second MKS locus (MKS2) to chromosome 11q13, by homozygosity mapping in seven families that do not show linkage to chromosome 17q21-q24 (maximum LOD score 4.41 at recombination fraction .01). Most interestingly, the affected fetuses of southern Tunisian ancestry shared a particular haplotype at loci D11S911 and D11S906, suggesting that a founder effect is involved. Our observation gives support to the clinical and genetic heterogeneity of MKS.

Abnormalities, Multiple↗
PubMed1998

Progressive osseous heteroplasia. Report of a family.

We report a case of progressive osseous heteroplasia in a female infant who had progressive ossification of the skin and deep connective tissues. Isolated dermal ossification is present in her father and younger sister suggesting an autosomal dominant mode of inheritance with variable expressivity or possible somatic mosaicism. This report of a family with progressive osseous heteroplasia contributes to the understanding of this uncommon genetic disorder, which must be distinguished from fibrodysplasia ossificans progressiva and Albright's hereditary osteodystrophy. The paucity of familial cases of progressive osseous heteroplasia currently limits the use of a genome-wide linkage analysis, but linkage exclusion analysis with promising candidate genes is a possibility.

Adult↗
PubMed1997

Severe brain and limb defects with possible autosomal recessive inheritance: a series of six cases and review of the literature.

Six fetuses with normal chromosomes were found to have severe craniofacial, limb, and visceral malformations during the second trimester of pregnancy. Two of these fetuses were monozygotic twins while a third one had a healthy dizygotic twin brother. A case with familial recurrence was also observed. Autopsy and skeletal radiographs suggested several diagnoses such as neural tube defect with limb defects or XK aprosencephaly. The development of these severe conditions in monozygotic twins and familial recurrence emphasize the difficulties of genetic counseling in such situations. These cases may suggest autosomal recessive inheritance.

Abnormalities, Severe Teratoid↗
PubMed1997

Prezygotic origin of the isochromosome 12p in Pallister-Killian syndrome.

Pallister-Killian syndrome is a rare disorder comprising multiple congenital anomalies, streaks of hypo(hyper)pigmentation, seizures, profound mental retardation, and the presence of an extra metacentric chromosome i(12)(p10), usually limited to skin fibroblasts. The mechanism and parental origin of the extra chromosome i(12)(p10) are unknown. Here, we present a girl with Pallister-Killian syndrome and the i(12)(p10) in 50% of cultured skin fibroblasts. Using microsatellite DNA markers of chromosome 12p, we detected 3 alleles--including 2 different alleles of maternal origin--in cultured skin fibroblasts, suggesting that the tetrasomy 12p is the result of a prezygotic event, with a nondisjunction event during maternal meiosis.

Abnormalities, Multiple↗
PubMed1997

Congenital lumbosacral lipomas.

Congenital lumbosacral lipomas can be responsible for progressive defects. The general feeling is that tethering of roots, filum, or cord probably explains this evolution, and that untethering of these structures could prevent late deterioration. Like the vast majority of neurosurgeons, we too have routinely and systematically operated on lumbosacral lipomas, even in the absence of neurological deficits. This policy stemmed from our belief that spontaneous neurological deterioration was frequent, recovery from preoperative deficits rare, and surgery both efficient and benign in nature. After 22 years of experience, we felt that it was necessary to review our series of 291 lipomas (38 lipomas of the filum and 253 of the conus) operated on from 1972 to 1994. To reassess the value of prophylactic surgery, we attempted an accurate evaluation of (1) the risk of pathology, (2) the risks involved in surgery, (3) the postoperative outcome with respect to preoperative deficits, and (4) the postoperative outcome in asymptomatic patients at 1 year and at maximum follow-up. Special attention was paid to 93 patients whose postoperative follow-up was more than 5 years (average 8.7, median 8, range 5-23 years). Of these 93 patients, 39 were asymptomatic preoperatively (7 with lipoma of the filum and 32 with lipoma of the conus). Lipomas of the filum and of the conus are entirely different lesions and were studied separately. In 6 cases prenatal diagnosis had been possible. The mean age at surgery was 6.4 years. Low back skin stigmata were present in 89.4% of cases. Preoperative neurological deficits existed in 57% of the patients and were congenital in 22%. Clinical signs and symptoms recorded were pain in 13.3% of the patients and/or neurological deficits affecting sphincter (52%), motor (27.6%) and sensory (22.4%) functions. Deficits were progressive in 22.4% of cases, slowly progressive in 58.8% of these and rapidly progressive in the remaining 41.2%. In 36 patients (13.2%) the lipomas were seen to grow either subcutaneously or intraspinally. Among these patients, 21 were infants, 2 were obese adolescents, and 10 were pregnant women. The metabolism of the fat within the lipomas was studied in 11 patients and found to be similar to that at other sites. Lipomas were associated with various other malformations, either intra- or extraspinal. These associated anomalies were rare in the case of lipomatous filum (5.2%) but frequent with lipomas of the conus, except for intracranial malformations (3.6%). Therapeutic objectives were spinal cord untethering and decompression, sparing of functional neural tissue and prevention of retethering. Procedures used to achieve these goals were subtotal removal of the lipoma, intraoperative monitoring, duroplasty, and sometimes closure of the placode. Histologically, lipomas consisted of normal mature fat. However, 77% of them also included a wide variety of other tissues, originating from ectoderm, mesoderm, or entoderm. This indicates that lipomas are either simple or complex teratomas. The results of the study are as follows. (1) Surgery was easy and safe when performed for treatment of lipomas of the filum (no complications), but difficult and hazardous in the case of lipomas of the conus (20% local, 3.9% neurological complications). (2) All types of deficit could be improved by surgery, which was beneficial in all cases of lipoma of the filum and 50% of cases of lipoma of the conus. (3) In asymptomatic patients long-term surgical results depended on the anatomical type of the lipoma. They were excellent in lipomas of the filum. In lipomas of the conus they were good in the short term but eroded with time. At more than 5 years of follow-up only 53.1% of the patients were still free of symptoms. (4) Reoperations were performed in 16 patients (5.5%), 5 (31.2%) of whom improved postoperatively, while in 7 (43.7%) progression stopped, in 3 (18.7%) deterioration continued and in 1 (6.2%) the condition was wor

Adolescent↗
PubMed1997

Nance-Horan syndrome: linkage analysis in 4 families refines localization in Xp22.31-p22.13 region.

Nance-Horan syndrome (NHS) is an X-linked disease characterized by severe congenital cataract with microcornea, distinctive dental findings, evocative facial features and mental impairment in some cases. Previous linkage studies have placed the NHS gene in a large region from DXS143 (Xp22.31) to DXS451 (Xp22.13). To refine this localization further, we have performed linkage analysis in four families. As the maximum expected Lod score is reached in each family for several markers in the Xp22.31-p22.13 region and linkage to the rest of the X chromosome can be excluded, our study shows that NHS is a genetically homogeneous condition. An overall maximum two-point Lod score of 9.36 (theta = 0.00) is obtained with two closely linked markers taken together. DXS207 and DXS1053 in Xp22.2. Recombinant haplotypes indicate that the NHS gene lies between DXS85 and DXS1226. Multipoint analysis yield a maximum Lod score of 9.45 with the support interval spanning a 15-cM region that includes DXS16 and DXS1229/365. The deletion map of the Xp22.3-Xp21.3 region suggests that the phenotypic variability of NHS is not related to gross rearrangement of sequences of varying size but rather to allelic mutations in a single gene, presumably located proximal to DXS16 and distal to DXS1226. Comparison with the map position of the mouse Xcat mutation supports the location of the NHS gene between the GRPR and PDHA1 genes in Xp22.2.

Abnormalities, Multiple↗
PubMed1997

An extension of the admixture test for the study of genetic heterogeneity in hereditary multiple exostoses.

Hereditary multiple exostoses (EXT) is an autosomal dominant disorder characterized by the presence of multiple cartilage-capped exostoses in the juxta-epiphyseal regions of the long bones. EXT is heterogeneous with at least three different locations currently having been identified on chromosomes 8, 11 and 19. We have tested a series of 29 EXT families for possible linkage to the three disease loci and estimated the probability of linkage of the disease to each locus in our series, by using an extension of the admixture test, which makes modelling of heterogeneous monogenic disease feasible. The maximum likelihood was obtained for proportions of 44%, 28% and 28% of families being linked to chromosome 8, 11 and 19, respectively. The a posteriori probability of linkage of the disease to EXT1, EXT2 and EXT3 was greater than 80% for 8/29, 5/29 and 3/29 families, respectively, and did not give evidence of a fourth locus for the disease. The present approach can be generalized to the investigation of genetic heterogeneity in other monogenic diseases, as it simultaneously estimates the location of each disease gene and the proportion of families linked to each locus.

Chromosomes, Human, Pair 11↗
PubMed1997

Mutations of the TWIST gene in the Saethre-Chotzen syndrome.

Saethre-Chotzen syndrome (acrocephalo-syndactyly type III, ACS III) is an autosomal dominant craniosynostosis with brachydactyly, soft tissue syndactyly and facial dysmorphism including ptosis, facial asymmetry and prominent ear crura. ACS III has been mapped to chromosome 7p21-22. Of interest, TWIST, the human counterpart of the murine Twist gene, has been localized on chromosome 7p21 as well. The Twist gene product is a transcription factor containing a basic helix-loop-helix (b-HLH) domain, required in head mesenchyme for cranial neural tube morphogenesis in mice. The co-localisation of ACS III and TWIST prompted us to screen ACS III patients for TWIST gene mutations especially as mice heterozygous for Twist null mutations displayed skull defects and duplication of hind leg digits. Here, we report 21-bp insertions and nonsense mutations of the TWIST gene (S127X, E130X) in seven ACS III probands and describe impairment of head mesenchyme induction by TWIST as a novel pathophysiological mechanism in human craniosynostoses.

Acrocephalosyndactylia↗
PubMed1997

Clustering of mutations responsible for branchio-oto-renal (BOR) syndrome in the eyes absent homologous region (eyaHR) of EYA1.

Branchio-oto-renal (BOR) syndrome is an autosomal dominant disorder, characterised by the association of branchial, otic and renal anomalies with variable degrees of severity. We have recently identified EYA1 , a human homologue of the Drosophila eyes absent gene, as the gene underlying this syndrome. The products of both genes share a highly conserved 271 amino acid C-terminal region (eyaHR). The eyaHR was also found in the products of two other human genes (EYA2 and EYA3), demonstrating the existence of a novel gene family. We report here on the complete genomic structure of EYA1. This gene consists of 16 coding exons and extends over 156 kb. It encodes various alternatively spliced transcripts differing only in their 5' regions. Sequence analysis of the entire EYA1 coding region was performed for 20 unrelated patients affected by BOR syndrome, and six novel mutations were identified. Among these mutations, two are missense mutations, highlighting amino acid residues essential for the function of the EYA1 protein, and one mutation comprises a de novo Alu insertion into an exon. This insertion presumably occurs by retrotransposition, and the mobile Alu element has a poly(A) tail that is unstable throughout generations. To date, 14 mutations have been detected in BOR patients, all of which are different. However, all the mutations are located within or in the immediate vicinity of the eyaHR; the significance of this clustering is discussed.

Amino Acid Sequence↗
PubMed1997

Ptosis, down-slanting palpebral fissures, hypertelorism, seizures and mental retardation: a possible new MCA/MR syndrome.

We present a family with six children of first cousin parents, in which three present with microcephaly, hypertelorism, down-slanting palpebral fissures, ptosis, a broad nasal tip, a short webbed neck, mental retardation and seizures. Two differential diagnosis, the Noonan and the Baraitser-Winter syndrome are discussed. The possibility of the description of a new MCA/MR syndrome is raised.

Abnormalities, Multiple↗