Search

Smith-Magenis syndrome (SMS) is caused by a microdeletion of 17p11.2 and comprises developmental and growth delay, facial abnormalities, unusual behavior and sleep problems. This phenotype may be due to haploinsufficiency of several contiguous genes. The human brain finger protein gene (ZNF179), a member of the RING finger protein family, has been isolated and mapped to 17p11.2. FISH analyses of metaphase or interphase chromosomes of 6 patients with SMS show that ZNF179 was deleted in one of the 2 homologs (17p11.2), indicating a possible association of the defect of this gene with the pathogenesis of SMS. Furthermore, using a prophase FISH ordering system, we sublocalized ZNF179 proximally to LLGL which lies on the critical region for SMS.

Recent studies have identified a new class of Prader-Willi syndrome (PWS) and Angelman syndrome (AS) patients who have biparental inheritance, but neither the typical deletion nor uniparental disomy (UPD) or translocation. However, these patients have uniparental DNA methylation throughout 15q11-q13, and thus appear to have a mutation in the imprinting process for this region. Here we describe detailed clinical findings of five AS imprinting mutation patients (three families) and two PWS imprinting mutation patients (one new family). All these patients have essentially the classical clinical phenotype for the respective syndrome, except that the incidence of microcephaly is lower in imprinting mutation AS patients than in deletion AS patients. Furthermore, imprinting mutation AS and PWS patients do not typically have hypopigmentation, which is commonly found in patients with the usual large deletion. Molecular diagnosis of these cases is initially achieved by DNA methylation analyses of the DN34/ZNF127, PW71 (D15S63), and SNRPN loci. The latter two probes have clear advantages in the simple molecular diagnostic analysis of PWS and AS patients with an imprinting mutation, as has been found for typical deletion or UPD PWS and AS cases. With the recent finding of inherited microdeletions in PWS and AS imprinting mutation families, our studies define a new class of these two syndromes. The clinical and molecular identification of these PWS and AS patients has important genetic counseling consequences.

Smith-Magenis syndrome (SMS) is a multiple congenital anomalies/mental retardation syndrome associated with deletion of band p11.2 of chromosome 17. The deletion is typically detected by high-resolution cytogenetic analysis of chromosomes from peripheral lymphocytes. Fluorescence in situ hybridization (FISH) has been previously used to rule out apparent mosaicism for del(17)(p11.2p11.2) indicated by routine cytogenetics. We now report mosaicism for del(17)(p11.2p11.2) in a child with SMS. The mosaicism had gone undetected during previous routine cytogenetic analysis. FISH analysis of peripheral lymphocytes as well as immortalized lymphoblasts using markers from 17p11.2 revealed that approximately 60% of cells carried the deletion. To our knowledge, this is the first case of SMS associated with mosaicism for del(17)(p11.2p11.2).

The polymorphic allele of the monoamine oxidase B (MAO-B) gene detected by polymerase chain reaction (PCR) and single-stranded conformation polymorphism (SSCP) was associated with Parkinson's disease (PD) in Caucasians. We characterized this polymorphic allele, allele 1, of the MAO-B gene using direct sequencing of PCR products. A single DNA substitution (G-A), resulting gain of Mae III restriction site was detected in intron 13 of the MAO-B gene. The allele associated with PD in Caucasians was twice as frequent as in healthy Japanese, but the association of the allele of the MAO-B gene was not observed in Japanese patients with PD.

Fragile X syndrome, one of the most common human genetic diseases, is characterized by a unique genetic mechanism which involves dynamic mutation in a heritable unstable DNA sequence, a p(CCG)n repeat, in the FRAXA locus. It has recently been suggested that a few founder chromosomes are responsible for most fragile X mutations in the Caucasian population. In order to investigate the origin of the fragile X mutations in the Japanese population, we analyzed haplotypes of the FRAXA locus in 40 unrelated fragile X chromosomes and 142 normal X chromosomes in Japanese males, by using two polymorphic AC repeats, FRAXAC1 and FRAXAC2, which flank the fragile site. This analysis provided evidence for founder fragile X chromosomes in the Japanese population, similar to that in Caucasians, although different haplotypes are involved. The distribution of normal allele size of the p(CCG)n repeat among the X chromosomes in the Japanese population is very similar to that reported for Caucasians, except that the most frequent copy number (n = 28) is one copy less than that in Caucasians and that there is an additional peak at 35 copies. There is significant correlation between FRAXAC alleles and the p(CCG)n repeat copy number in non-fragile X chromosomes, however, alleles with more than 31 copies of the p(CCG)n repeat do not segregate with either of the fragile X common FRAXAC haplotypes.

We report on 2 Japanese patients (a 3-year-old girl and an 20-month-old boy) with the Weaver syndrome. The clinical manifestations are mild mental retardation, overgrowth with accelerated bone age, minor facial anomalies including broad forehead, mild hypertelorism, depressed nasal bridge, accentuated philtrum, micrognathia and large ears, and unique behavior characteristics with some social withdrawal. The nosology of the Weaver and Simpson-Golabi-Behmel syndromes is discussed.

We report clinical and cytogenetic findings of 4 children (2 boys and 2 girls) with the Smith-Magenis syndrome. All 4 patients had an interstitial deletion of 17p: del(17) (p11.2p11.2). Their clinical manifestations included brachycephaly, midface hypoplasia, prognathism, upper lip eversion, short and broad hands with short fingers, clinodactyly of the fifth fingers, fingertip pads, moderate mental retardation, and behavior problems. Analysis of the metacarpophalangeal pattern profiles in patient 2 showed progressive shortness from the metacarpals to the proximal, middle, and the distal phalanges. The fingerpads observed in all 4 patients have hitherto been noted in only one of 26 previously reported patients with the syndrome. These findings serve as a useful clue to the diagnosis of the syndrome.

We describe a brother and sister with Hirschsprung disease, hypotonia, and ptosis. Their condition resembles that in 2 sibs reported by Goldberg and Shprintzen. We conclude that the clinical characteristics in 8 reported cases with similar clinical manifestations represent a distinct autosomal recessive syndrome, Goldberg-Shprintzen syndrome.

A new familial cases of the Cohen syndrome in two brothers of one-half second-cousin parents is reported. Typical clinical manifestations of the syndrome; i.e., mental deficiency, hypotonia, characteristic facial appearance, long, narrow hands and feet with elongated fingers, and mottled retinae were present in both patients. Both patients also had leukopenia. Clinical manifestations of the Cohen syndrome in patients are highly variable, and mottled retina has been observed in 22 of 87 patients (25%). However, an association of mottled retina in patients with the Cohen syndrome is likely to be related to the families and ethnic groups. Among 19 familial cases, mottled retina was observed in all affected sibs from five families, but in 13 families none of the affected sibs had the mottled retina. All Finnish patients had the mottled retina, but this was noted in only one of 39 Jewish patients. Based on these data, we hypothesize that two alleles at the gene locus for the Cohen syndrome exhibit different clinical manifestations: one is a Finnish type with mottled retina, and the other is a Jewish type without retinal anomalies.