The cDNA for a murine galactocerebrosidase was isolated from a murine testis cDNA library on the basis of its homology with the cDNA for human galactocerebrosidase and a PCR method was used to clone the 5′ end. It has a 2,278‐nucleotide sequence including a 2,004‐nucleotide open reading frame, which encodes 668 amino acid residues. The identity between the human and murine amino acid sequences was very high, being calculated to be 84%. Sequencing of cDNA from liver of the twitcher mouse revealed a nonsense mutation at codon 339 (TGG → TGA). The most abundant mRNA of the murine galactocerebrosidase gave a 3.6‐kb band, which was not detected in twitcher mice. This suggests that the cDNA (2,278 bp) we characterized represents a minor species generated by an alternate poly(A) signal and that most of the mRNA has a much longer 3′‐untranslated region. Genome analysis revealed that this mutation was homozygous in the twitcher and heterozygous in the carrier but was not present in normal mice. The normal mouse cDNA but not the mutant cDNA of the galactocerebrosidase transfected into COS1 cells gave rise to an increase in enzymatic activity. We concluded that this mutation results in the deficiency of galactocerebrosidase in the twitcher mouse.

Sotos syndrome (SoS) is an autosomal dominant overgrowth syndrome with characteristic craniofacial dysmorphic features and various degrees of mental retardation. We previously showed that haploinsufficiency of the NSD1 gene is the major cause of SoS, and submicroscopic deletions at 5q35, including NSD1, were found in about a half (20/42) of our patients examined. Since the first report, an additional 70 SoS cases consisting of 53 Japanese and 17 non-Japanese have been analyzed. We found 50 microdeletions (45%) and 16 point mutations (14%) among all the 112 cases. A large difference in the frequency of microdeletions between Japanese and non-Japanese patients was noted: 49 (52%) of the 95 Japanese patients and only one (6%) of the 17 non-Japanese had microdeletions. A sequence-based physical map was constructed to characterize the microdeletions. Most of the microdeletions were confirmed to be identical by FISH analysis. We identified highly homologous sequences, i.e., possible low copy repeats (LCRs), in regions flanking proximal and distal breakpoints of the common deletion, This suggests that LCRs may mediate the deletion. Such LCRs seem to be present in different populations. Thus the different frequency of microdeletions between Japanese and non-Japanese cases in our study may have been caused by patient-selection bias.

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Purpose: We tested the hypothesis that Sotos syndrome (SoS) due to the common deletion is a contiguous gene syndrome incorporating plasma coagulation factor twelve (FXII) deficiency. The relationship between FXII activity and the genotype at a functional polymorphism of the FXII gene was investigated. Methods: A total of 21 patients including those with the common deletion, smaller deletions, and point mutations, and four control individuals were analyzed. We examined FXII activity in patients and controls, and analyzed their FXII 46C/T genotype using direct DNA sequencing.Results: Among 10 common deletion patients, seven patients had lower FXII activity with the 46T allele of the FXII gene, whereas three patients had normal FXII activity with the 46C allele. Two patients with smaller deletions, whose FXII gene is not deleted had low FXII activity, but one patient with a smaller deletion had normal FXII. Four point mutation patients and controls all had FXII activities within the normal range. Conclusion: FXII activity in SoS patients with the common deletion is predominantly determined by the functional polymorphism of the remaining hemizygous FXII allele. Thus, Sotos syndrome is a contiguous gene syndrome incorporating coagulation factor twelve (FXII) deficiency. Genet Med 2005:7(7):479-483.

Sotos syndrome (SoS) is characterized by pre- and postnatal overgrowth with advanced bone age; a dysmorphic face with macrocephaly and pointed chin; large hands and feet; mental retardation; and possible susceptibility to tumors. It has been shown that the major cause of SoS is haploinsufficiency of the NSD1 gene at 5q35, because the majority of patients had either a common microdeletion including NSD1 or a truncated type of point mutation in NSD1. In the present study, we traced the parental origin of the microdeletions in 26 patients with SoS by the use of 16 microsatellite markers at or flanking the commonly deleted region. Deletions in 18 of the 20 informative cases occurred in the paternally derived chromosome 5, whereas those in the maternally derived chromosome were found in only two cases. Haplotyping analysis of the marker loci revealed that the paternal deletion in five of seven informative cases and the maternal deletion in one case arose through an intrachromosomal rearrangement, and two other cases of the paternal deletion involved an interchromosomal event, suggesting that the common microdeletion observed in SoS did not occur through a uniform mechanism but preferentially arose prezygotically.

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The sphingolipidoses are generally understood to be lysosomal lipid storage diseases due to genetic enzymic defects of sphingolipid metabolism. However, the molecular mechanisms that lead to the clinical and pathological manifestations rernain largely obscure. Recent morphological and biochemical studies in neuronal storage diseases (Purpura and Suzuki, 1976) and animal models of gangliosidoses (Wood et al., 1985) suggested that altered membrane structure could be one of the causes of neuronal dysfunction. To understand the mechanism causing neurological dysfunctions in sphingolipidoses, clarification of the synthesis, translocation and insertion of sphingolipids in the different subcellular components in normal and pathological states is essential. This paper reports the metabolism of cerebroside sulphate (CS) and the subcellular distribution of its metabolite in cultured skin fibroblasts from normal control, metachromatic leukodystrophy (MLD; McKusick 25010), globoid cell leukodystrophy (GLD; McKusick 24520) and Farber disease (McKusick 22800). MATERIALS AND METHODS[1-14C]Stearic acid-labelled cerebroside sulphate (14C-CS) was prepared according to the methods of Dubois et al. (1980). Fibroblast cultures from controls, and patients with MLD, GLD and Farber disease, were grown and maintained as described previously (Inui et al., 1985). Feeding experiments of 14C-CS were undertaken as described by Kudoh and Wenger (1982) with minor modifications. After a 24h pulse, cells were harvested by trypsin (0.25%) and washed once with 1% bovine serum albumin in phosphate buffered saline (PBS) and twice with PBS. Cell pellets were suspended in 0.5 mL of 0.25 tool L -~ sucrose solution containing 1 mmol L -~ EDTA adjusted to pH7.0 with 1 molL -1 KOH and homogenized with 10 strokes in a Dual i homogenizer. Then the homogenate was centrifuged at 800g 293Journal of Inherited Metabolic Disease. ISSN 0141-8955.

Abnormality in the beta-hexosaminidase alpha gene underlying the clinical phenotype of a Lebanese patient with a juvenile form of Tay-Sachs disease has been studied. Clinical features were progressive spasticity, ataxia, and cognitive decline. The protein coding sequence of several beta-hexosaminidase alpha-chain complementary DNAs isolated by polymerase chain reaction was completely normal except for a G-to-A transition at nucleotide position 1511 within exon 13, which resulted in substitution of the normal arginine 504 (CGC) with histidine (CAC). Although the patient was from a first-cousin marriage, she was heterozygous for this mutation. The abnormality in the other allele, which is carried by the father, was not identified, except that it is neither of the two mutations responsible for the infantile Jewish Tay-Sachs disease. Biosynthetic and immunoprecipitation studies in cultured fibroblasts showed synthesis of the alpha-chain precursor, but the mature form of the alpha-subunit was not detected.