Low vertebral cancellous bone density in peripubertal girls with Turner's syndrome and boys with hypogonadism.

OBJECTIVE: To characterize the changes of vertebral cancellous bone density in children with hypogonadism. STUDY DESIGN: Quantitative computed tomography (QCT) values of vertebral cancellous bone in 21 girls with Turner's syndrome, 12 boys with hypogonadism, and 46 age-matched controls (24 boys, 22 girls) were studied. The subjects were divided into the following subgroups by the age (year) at the time of the measurement: A. 4-6.9; B. 7-9.9; C. 10-12.9. RESULTS: QCT values for Turner's syndrome vs control girls in the same age groups (A, B, and C) were (mean +/- SD) 226 +/- 36 vs 216 +/- 31 (NS), 193 +/- 29 vs 220 +/- 33 (NS), and 177 +/- 32 vs 217 +/- 17 (p < 0.01) mg/cm3, respectively. Those for boys with hypogonadism vs control boys (A, B, and C) were 236 +/- 15 vs 240 +/- 12 (NS), 187 +/- 21 vs 225 +/- 28 (p < 0.05), and 172 +/- 11 vs 216 +/- 26 (p < 0.0001) mg/cm, respectively. The cross-sectional data for Turner's syndrome and boys with hypogonadism had significant negative correlation with chronological age (r = 0.59; p < 0.001). CONCLUSION: These results showed that vertebral cancellous bone density in children with hypogonadism began to decrease during the peripubertal period in contrast to the constant values in controls, suggesting that a small amount of gonadal steroid in healthy children has an important role in maintaining normal bone density.

Mother and daughter with 45,X/46,X,r(X)(p22.3q28) and mental retardation: analysis of the X-inactivation patterns.

We report on a mother and daughter both with a 45,X/46,X,r(X)(p22. 3q28) karyotype and mental retardation. Fluorescence in situ hybridization (FISH) and microsatellite analyses for 14 loci/region at Xp22.3 and seven loci/region at Xq28 indicated that the ring X chromosome was missing a roughly 12-Mb region from Xp22.3 with the breakpoint between DXS85 and DXS9972, and another region of less than 100 kb from Xq28 with the breakpoint distal to the region defined by the FISH probe c8.2/1. X-inactivation analysis, using the methylation status of the AR gene (exon 1) as an indicator, showed that the normal and ring X chromosomes in the X,r(X)(p22.3q28) cell lineage were randomly inactivated. The Xp22.3 deleted region partially overlaps with the regional intervals of MRX19, MRX21, MRX24, MRX37, MRX43, and MRX49 associated with heterozygote manifestation. Therefore, it is likely that one or more of these MRX genes, subject to X-inactivation, are lost from the ring X chromosome, and that reduced expression of the MRX gene(s) caused by random X-inactivation has resulted in mental retardation in the mother and daughter.

A case of congenital hypopituitarism: difficulty in the diagnosis of ACTH deficiency due to high serum cortisol levels from a hypothyroid state.

A three-month-old boy presented congenital hypopituitarism in which the hypothyroid state masked ACTH deficiency. Multiple anterior pituitary hormone deficiencies, including ACTH, were finally confirmed. High basal serum cortisol levels (up to 45.1 microg/dl) were observed during a stressful episode before L-thyroxine replacement therapy was started. Decreased morning serum cortisol levels (5.0 microg/dl or below) were observed on the sixth day of L-thyroxine replacement therapy despite mild hypoglycemia (lowest serum glucose level of 50 mg/dl). ACTH deficiency was then confirmed by insulin-induced hypoglycemia test (peak serum cortisol level of 4.9 microg/dl). The present findings showed that serum cortisol levels can be high during a stressful episode in an infant with ACTH deficiency and a coexisting hypothyroid state. Thus, the diagnostic evaluation of adrenal function soon after L-thyroxine replacement therapy is important in order to verify a possible subclinical ACTH deficiency, even in the presence of high serum cortisol levels before L-thyroxine replacement therapy.

Identification of the mutations in the T-protein gene causing typical and atypical nonketotic hyperglycinemia.

We have investigated the molecular lesions of T-protein deficiency causing typical or atypical nonketotic hyperglycinemia (NKH) in two unrelated pedigrees. A patient with typical NKH was identified as being homozygous for a missense mutation in the T-protein gene, a G-to-A transition leading to a Gly-to-Asp substitution at amino acid 269 (G269D). Sibling patients of a second family with atypical NKH had two different missense mutations in the T-protein gene (compound heterozygote), a G-to-A transition leading to a Gly-to-Arg substitution at amino acid 47 (G47R) in one allele, and a G-to-A transition leading to an Arg-to-His substitution at amino acid 320 (R320H) in the other allele. Gly 269 is conserved in T-proteins of various species, even in E. coli, whereas Gly 47 and Arg 320 are replaced by Ala and Leu, respectively, in E. coli. The mutation occurring in more conservative amino acid residues thus results in more deleterious damage to the T-protein, and gives the severe clinical phenotype, viz., typical NKH.

Structure and chromosomal localization of the aminomethyltransferase gene (AMT)

The gene for human aminomethyltransferase (AMT), also known as the T-protein of the glycine cleavage system, was isolated from a human placental cosmid library and examined by restriction mapping, polymerase chain reaction analysis, and DNA sequencing. The gene is about 6 kb in length and consists of nine exons. The 5'-flanking region of the gene lacks typical TATAA sequence but has a single defined transcription initiation site detected by the primer extension method. Two putative glucocorticoid-responsive elements and a putative thyroid hormone-responsive element are present. The AMT gene was assigned to subband 3p21.2-p21.1 by fluorescence in situ hybridization.

De novo mutation of the myelin P0 gene in Dejerine-Sottas disease (hereditary motor and sensory neuropathy type III).

We have investigated the myelin P0 gene on chromosome 1 as a candidate gene in two sporadic cases with Dejerine-Sottas disease or hereditary motor and sensory neuropathy (HMSN) type III. We found different mutations, a cysteine substitution for serine 63 in the extracellular domain and an arginine substitution for glycine 167 in the transmembrane domain. The patients were genetically heterozygous for the normal allele and the mutant allele, which was absent in their parents and in one hundred unrelated, healthy controls. The results strongly suggest that a de novo dominant mutation of the P0 gene is responsible for at least some sporadic cases of Dejerine-Sottas disease.

Isolation and sequence determination of cDNA encoding human T-protein of the glycine cleavage system.

We present the full-length cDNA sequence of human T-protein of the glycine cleavage system. Overlapping cDNA clones were isolated by screening human liver cDNA libraries with bovine T-protein cDNA. The 1209 base pair open reading frame encodes 403 amino acid precursor protein, and the deduced amino acid sequence of the mature peptide shows 90 and 68% homology to that of bovine and chicken counterpart, respectively. RNA blot analysis of human liver transcripts and Southern blot analysis of human genomic DNA confirm that human T-protein is encoded by a single gene.

Localization of PMP-22 gene (candidate gene for the Charcot-Marie-Tooth disease 1A) to band 17p11.2 by direct R-banding fluorescence in situ hybridization.

We mapped PMP-22 gene, candidate gene for the Charcot-Marie-Tooth disease (CMT) 1A, by direct R-banding fluorescence in situ hybridization. The signals of PMP-22 probe were localized to chromosome band 17p11.2. The present result was within the map position of the CMT 1A gene by genetic linkage analysis, and strongly indicated that PMP-22 gene is a candidate gene for the CMT 1A.

Isolation and sequence determination of cDNA encoding PMP-22 (PAS-II/SR13/Gas-3) of human peripheral myelin.

A full length cDNA of PMP-22 (PAS-II/SR13/Gas-3) of peripheral myelin has been isolated from a cDNA library of human fetus spinal cord. The clone is 1823 base pairs (bp) in length and contains a 480 bp open reading frame encoding a polypeptide of 160 residues. The deduced amino acid sequence is highly homologous to PMP-22 from bovine (PAS-II), rat (SR13) and mouse (Gas-3).

Isolation and sequence determination of cDNA encoding P2 protein of human peripheral myelin.

A full length cDNA of P2 protein of peripheral myelin has been isolated from a cDNA library of human fetus spinal cord. The clone is 2150 base pairs (bp) in length and contains a 393 bp open reading frame encoding a polypeptide of 131 residues. The deduced amino acid sequence is highly homologous to P2 protein from other species.

Isolation and sequence determination of cDNA encoding the major structural protein of human peripheral myelin.

A full length cDNA of the major structural protein of peripheral myelin (P0 protein) has been isolated from a cDNA library of human fetus spinal cord. The clone is 1948 base pairs (bp) in length and contains a 744 bp open reading frame encoding a polypeptide of 248 residues including 29 signal peptide. The deduced amino acid sequence is highly homologous to P0 protein from other species.