Abnormal myocardial lipid composition in an infant with type II glutaric aciduria

We have analyzed the myocardial lipids of an infant with glutaric aciduria type II (GAII) who died from sudden cardiac failure and of five infants who died suddenly from indeterminate causes (sudden infant death syndrome, SIDS). Histology of the SIDS hearts was normal, but there was marked fatty deposition in the GAII heart. Fatty acid composition of myocardial lipids was determined by thin-layer chromatography-gas-liquid chromatography. Total lipid was elevated 20-fold in the GAII heart. Of total fatty acids, 75% was derived from phospholipids in SIDS heart and 89% from neutral lipids in GAII heart. Increased levels of free oleic acid and a 6-fold elevation in the (n-6)/(n-3) fatty acid ratio in phospholipid were noted in GAII heart compared to SIDS hearts.     

Molecular genetic study of glutaric aciduria,type I: Identification of a novel mutation

Glutaric acidemia type I (GA-1) is an inborn error of metabolism due to deficiency of glutaryl-CoA dehydrogenase (GCDH), which catalyzes the conversion of glutaryl-CoA to crotonyl-CoA. GA-1 occurs in about 1 in 100 000 infants worldwide. The GCDH gene is on human chromosome 19p13.2, spans about 7 kb and comprises 11 exons and 10 introns. Tandem mass spectrometry (MS/MS) was used for clinical diagnosis in a proband from Iran with GA-1. Sanger sequencing was performed using primers specific for coding exons and exon-intron flanking regions of the GCDH gene in the proband. Cosegregation analysis and in silico assessment were performed to confirm the pathogenicity of the candidate variant. A novel homozygous missense variant c.1147C > A (p.Arg383Ser) in exon 11 of GCDH was identified. Examination of variant through in silico software tools determines its deleterious effect on protein in terms of function and stability. The variant cosegregates with the disease in family. In this study, the clinical and molecular aspects of GA-1 were investigated, which showed one novel mutation in the GCDH gene in an Iranian patient. The variant is categorized as pathogenic according to the the guideline of the American College of Medical Genetics and Genomics (ACMG) for variant interpretation. This mutation c.1147C > A (p.Arg383Ser) may also be prevalent among Iranian populations.     

X-linked myoclonus epilepsy explained as a maternally inherited mitochondrial disorder

A family with myoclonus epilepsy has been described previously as suffering from an X-linked disorder, because at least four males were affected, and only mild and variable symptoms were seen in some female carriers. In this family, we have now identified a mitochondrial AG (8344) heteroplasmic point mutation. This point mutation has been described in families with maternally inherited myoclonus epilepsy and ragged red fibers. The degree of severity of the disorder in the different family members was reflected in the relative quantity of mutated mitochondrial DNA. It is concluded that the mode of inheritance in this family is not X-linked but maternal.     

Mass spectrometric analysis of metabolite excretion in five Japanese patients with the late-onset form of glutaric aciduria type II.

The variability of clinical and biochemical features in five Japanese patients with the late-onset form of glutaric aciduria type II (GAII) was studied using mass spectrometric procedures. The age at onset ranged from 5 months to five years, presenting acute episodes such as lethargy, hypotonia, hyperammonaemia, hypoglycaemia or Reye's syndrome-like illness, while one of the five cases was asymptomatic at 1 year of age. Organic acid analysis as oxime-trimethylsilyl derivatives by gas chromatography/mass spectrometry revealed the presence of several abnormalities characteristic of GAII in clinically asymptomatic conditions of three patients but not of the two others. Quantitative acylglycine analysis using a stable isotope dilution method and qualitative acylcarnitine analysis by fast atom bombardment mass spectrometry provided diagnostic information in all five patients, regardless of their clinical conditions. However, significant differences in the respective metabolite profiles as well as in their clinical pictures were noted. Although an increased excretion of both isovalerylglycine and isovalerylcarnitine was found in four patients, the fifth showed normal isovalerylglycine excretion during both the acute stage and in remission, despite the increased amount of isovalerylcarnitine in urine. From these results, it was suggested that the variations in clinical severity and metabolite excretion among GAII patients may be attributed not only to the residual enzyme activity at the defective site but also to differences in the capability to conjugate accumulated acyl-coenzyme A.     

The human glutaryl-CoA dehydrogenase gene: report of intronic sequences and of 13 novel mutations causing glutaric aciduria type I

Glutaric acidemia type I (GAI) (McKusick 231670) is an autosomal recessive disease affecting the catabolism of the amino acids lysine, hydroxylysine and tryptophan, caused by a defect in the gene encoding glutaryl-coenzyme A dehydrogenase (GCDH) and associated with severe neurological symptoms. Several pathogenic mutations in GCDH have been reported to cause GAI. One mutation, R402W, is more common than the others, which seem to be private” mutations. Here we report the entire sequences of introns 1, 2, 3, 6, 7, 8 and 9, and part of those of introns 4, 5 and 10 as well as 21 different mutations in 20 patients with GAI, corresponding to 38 out of 40 alleles. Received: 29 September / Accepted: 4 December 1997     

Acute renal proximal tubule alterations during induced metabolic crises in a mouse model of glutaric aciduria type 1

The metabolic disorder glutaric aciduria type 1 (GA1) is caused by deficiency of the mitochondrial glutaryl-CoA dehydrogenase (GCDH), leading to accumulation of the pathologic metabolites glutaric acid (GA) and 3-hydroxyglutaric acid (3OHGA) in blood, urine and tissues. Affected patients are prone to metabolic crises developing during catabolic conditions, with an irreversible destruction of striatal neurons and a subsequent dystonic–dyskinetic movement disorder. The pathogenetic mechanisms mediated by GA and 3OHGA have not been fully characterized. Recently, we have shown that GA and 3OHGA are translocated through membranes via sodium-dependent dicarboxylate cotransporter (NaC) 3, and organic anion transporters (OATs) 1 and 4. Here, we show that induced metabolic crises in Gcdh^?/? mice lead to an altered renal expression pattern of NaC3 and OATs, and the subsequent intracellular GA and 3OHGA accumulation. Furthermore, OAT1 transporters are mislocalized to the apical membrane during metabolic crises accompanied by a pronounced thinning of proximal tubule brush border membranes. Moreover, mitochondrial swelling and increased excretion of low molecular weight proteins indicate functional tubulopathy. As the data clearly demonstrate renal proximal tubule alterations in this GA1 mouse model during induced metabolic crises, we propose careful evaluation of renal function in GA1 patients, particularly during acute crises. Further studies are needed to investigate if these findings can be confirmed in humans, especially in the long-term outcome of affected patients.     

Brachytelephalangic chondrodysplasia punctata: a possible X-linked recessive form

Summary The author describes four cases of chondrodysplasia punctata with an hypoplasia of the distal phalange of the fingers. In these cases, growth disturbance is moderate without asymmetry of the limbs, and the facial dysmorphism is similar to that found in Binder's maxillo-facial dysostosis. The phalangeal anomaly is very important for the diagnosis of chondrodysplasia punctata at an age when epiphyseal stippling is no longer present. The relationship of this form of chondro-dysplasia with cases in which there is a deletion of the terminal short arm of the X chromosome is discussed. A possible hypothesis is that this form, which is always observed in males, is secondary to an isolated mutation of the Xp localized gene.     

A new mutation in the type II hair cortex keratin hHb1 involved in the inherited hair disorder monilethrix

Monilethrix is a rare dominant hair disease characterized by beaded or moniliform hair which results from the periodic thinning of the hair shaft and shows a high propensity to excess weathering and fracturing. Several cases of monilethrix have been linked to the type II keratin gene cluster on chromosome 12q13 and causative heterozygous mutations of a highly conserved glutamic acid residue (Glu 410 Lys and Glu 410 Asp) in the helix termination motif of the type II hair keratin hHb6 have recently been identified in monilethrix patients of two unrelated families. In the present study, we have investigated two further unrelated monilethrix families as well as a single case. Affected members of one family and the single patient exhibited the prevalent hHb6 Glu 410 Lys mutation. In the second family, we identified in affected individuals a lysine substitution of the corresponding glutamic acid residue, Glu 403, in the type II hair keratin hHb1, suggesting that this site represents a mutational hotspot in these highly related type II hair keratins. Both hHb1 and hHb6 are largely coexpressed in cortical trichocytes of the hair shaft. This indicates that monilethrix is a disease of the hair cortex. Received: 24 June 1997 / Accepted: 30 July 1997     

Waisman syndrome, a human X-linked recessive basal ganglia disorder with mental retardation: localization to Xq27.3-qter.

Linkage of the gene responsible for an X-linked early onset parkinsonism disorder with mental retardation (McKusick 311510) to DNA probes that detect restriction fragment length polymorphisms is described. The disease gene is linked to the F8C gene, and to DNA probes detecting polymorphic loci DXS52, DXS15, DXS134, and DXS374 with maximum lod scores at theta = 0 of 5.08, 5.19, 5.00, 5.03, and 4.46, respectively. Multipoint linkage analysis gives a maximum multipoint lod score of 6.75 at the F8C gene. This places the disease gene in chromosomal region Xq27.3-qter.     

Stable-isotope dilution gas chromatography-mass spectrometric measurement of 3-hydroxyglutaric acid, glutaric acid and related metabolites in body fluids of patients with glutaric aciduria type 1 found in newborn screening

We developed a simple and sensitive stable-isotope dilution method for the quantification of 3-hydroxyglutaric acid (3HGA) and glutaric acid (GA) in body fluids. In our method, tert-butyldimethylsilyl (tBDMS) derivatives of 3HGA and GA were measured with a conventional electron-impact ionization (EI) mode in gas chromatography-mass spectrometry (GC-MS). The control values for 3HGA in nmol/ml were 0.15+/-0.08 (serum; n=10) and 0.07+/-0.03 (CSF; n=10). In addition, glutarylcarnitine and free carnitine were quantified by electrospray tandem mass spectrometry. Using these methods, we monitored 3HGA, GA, and glutarylcarnitine in the body fluids of three patients with glutaric aciduria type 1 found during newborn screening. None of the patients had experienced neurological strokes, which are possibly caused by the accumulation of 3HGA, at 15-24 months of age under a disease-specific treatment, including carnitine supplementation. Our data showed that 3HGA levels were relatively high in some serum samples with lower glutarylcarnitine and carnitine levels, suggesting that carnitine supplementation may play a role in preventing the accumulation of 3HGA in patients with this disease.     

Genetic mapping of glutaric aciduria, type 3, to chromosome 7 and identification of mutations in c7orf10

While screening Old Order Amish children for glutaric aciduria type 1 (GA1) between 1989 and 1993, we found three healthy children who excreted abnormal quantities of glutaric acid but low 3-hydroxyglutaric acid, a pattern consistent with glutaric aciduria type 3 (GA3). None of these children had the GCDH c.1262C→T mutation that causes GA1 among the Amish. Using single-nucleotide polymorphism (SNP) genotypes, we identified a shared homozygous 4.7 Mb region on chromosome 7. This region contained 25 genes including C7orf10, an open reading frame with a putative mitochondrial targeting sequence and coenzyme-A transferase domain. Direct sequencing of C7orf10 revealed that the three Amish individuals were homozygous for a nonsynonymous sequence variant (c.895C→T, Arg299Trp). We then sequenced three non-Amish children with GA3 and discovered two nonsense mutations (c.322C→T, Arg108Ter, and c.424C→T, Arg142Ter) in addition to the Amish mutation. Two pathogenic alleles were identified in each of the six patients. There was no consistent clinical phenotype associated with GA3. In affected individuals, urine molar ratios of glutarate to its derivatives (3-hydroxyglutarate, glutarylcarnitine, and glutarylglycine) were elevated, suggesting impaired formation of glutaryl-CoA. These observations refine our understanding of the lysine-tryptophan degradation pathway and have important implications for the pathophysiology of GA1.     

Transport and distribution of 3-hydroxyglutaric acid before and during induced encephalopathic crises in a mouse model of glutaric aciduria type 1

Glutaric aciduria type 1 (GA1) is caused by the deficiency of glutaryl-CoA dehydrogenase (GCDH). Affected patients are prone to the development of encephalopathic crises during an early time window with destruction of striatal neurons and a subsequent irreversible movement disorder. 3-Hydroxyglutaric acid (3OHGA) accumulates in tissues and body fluids of GA1 patients and has been shown to mediate toxic effects on neuronal as well as endothelial cells. Injection of (3H)-labeled into 6 week-old Gcdh(-/-) mice, a model of GA1, revealed a low recovery in kidney, liver, or brain tissue that did not differ from control mice. Significant amounts of 3OHGA were found to be excreted via the intestinal tract. Exposure of Gcdh(-/-) mice to a high protein diet led to an encephalopathic crisis, vacuolization in the brain, and death after 4-5 days. Under these conditions, high amounts of injected 3H-3OHGA were found in kidneys of Gcdh(-/-) mice, whereas the radioactivity recovered in brain and blood was reduced. The data demonstrate that under conditions mimicking encephalopathic crises the blood-brain barrier appears to remain intact.     

An X-linked recessive mutation producing cleft palate, crooked tail, and polydactyly in mice

Palate-tail-digits abnormality (ptd) is a new X-linked recessive mutation affecting the morphogenesis of the mouse. It maps proximal to Tabby. Hemizygous males and homozygous females exhibit skeletal malformations of the tail, polydactyly of the hind feet, and in about 60% of the cases a cleft palate. A very high level of postnatal mortality is observed even among the mutants without a cleft palate.     

In vitro probe acylcarnitine profiling assay using cultured fibroblasts and electrospray ionization tandem mass spectrometry predicts severity of patients with glutaric aciduria type 2

Glutaric aciduria type 2 (multiple acyl-CoA dehydrogenase deficiency, MAD) is a multiple defect of mitochondrial acyl-CoA dehydrogenases due to a deficiency of electron transfer flavoprotein (ETF) or ETF dehydrogenase. The clinical spectrum are relatively wide from the neonatal onset, severe form (MAD-S) to the late-onset, milder form (MAD-M). In the present study, we determined whether the in vitro probe acylcarnitine assay using cultured fibroblasts and electrospray ionization tandem mass spectrometry (MS/MS) can evaluate their clinical severity or not. Incubation of cells from MAD-S patients with palmitic acid showed large increase in palmitoylcarnitine (C16), whereas the downstream acylcarnitines; C14, C12, C10 or C8 as well as C2, were extremely low. In contrast, accumulation of C16 was smaller while the amount of downstream metabolites was higher in fibroblasts from MAD-M compared to MAD-S. The ratio of C16/C14, C16/C12, or C16/C10, in the culture medium was significantly higher in MAD-S compared with that in MAD-M. Loading octanoic acid or myristic acid led to a significant elevation in C8 or C12, respectively in MAD-S, while their effects were less pronounced in MAD-M. In conclusion, it is possible to distinguish MAD-S and MAD-M by in vitro probe acylcarnitine profiling assay with various fatty acids as substrates. This strategy may be applicable for other metabolic disorders.     

牛蜘蛛腿综合征: 一种骨骼系统畸形遗传疾病

牛蜘蛛腿综合征(Arachnomelia syndrome, AS)是主要在欧洲瑞士褐牛和德系西门塔尔牛群体中出现的一种以骨骼畸形为病理特征的先天致死性遗传病, 呈孟德尔隐性遗传。文章通过对AS的发现历史、病理特点、遗传规律以及AS在欧洲瑞士褐牛和德系西门塔尔牛两个品种中分子机理研究进展进行综述, 并从骨骼发育、比较基因组学两方面对西门塔尔牛AS的定位区段进行候选基因的预测, 为以后筛查影响该病的基因及其突变以及建立检测方法提供一定的依据。     

Definitive evidence for an autosomal recessive form of hypohidrotic ectodermal dysplasia clinically indistinguishable from the more common X-linked disorder.

A crucial issue in genetic counseling is the recognition of nonallelic genetic heterogeneity. Hypohidrotic (anhidrotic) ectodermal dysplasia (HED), a genetic disorder characterized by defective development of hair, teeth, and eccrine sweat glands, is usually inherited as an X-linked recessive trait mapped to the X-linked ectodermal dysplasia locus, EDA, at Xq12-q13.1. The existence of an autosomal recessive form of the disorder had been proposed but subsequently had been challenged by the hypothesis that the phenotype of severely affected daughters born to unaffected mothers in these rare families may be due to marked skewing of X inactivation. Five families with possible autosomal recessive HED have been identified, on the basis of the presence of severely affected females and unaffected parents in single sibships and in highly consanguineous families with multiple affected family members. The disorder was excluded from the EDA locus by the lack of its cosegregation with polymorphic markers flanking the EDA locus in three of five families. No mutations of the EDA gene were detected by SSCP analysis in the two families not excluded by haplotype analysis. The appearance of affected males and females in autosomal recessive HED was clinically indistinguishable from that seen in males with X-linked HED. The findings of equally affected males and females in single sibships, as well as the presence of consanguinity, support an autosomal recessive mode of inheritance. The fact that phenotypically identical types of HED can be caused by mutations at both X-linked and autosomal loci is analogous to the situation in the mouse, where indistinguishable phenotypes are produced by mutations at both X-linked (Tabby) and autosomal loci (crinkled and downless).     

An interstitial deletion in Xp22.3 in a family with X-linked recessive chondrodysplasia punctata and short stature

Summary In a four-generation family, chondrodysplasia punctata was found in a boy and one of his maternal uncles. These two patients also have short stature, as do all female members of the family. DNA molecular analysis of the pseudoautosomal and Xp22.3-specific loci revealed the presence of an interstitial deletion that cosegregates with the phenotypic abnormalities. The proximal breakpoint of this deletion was located distal to the DXS31 locus and the distal breakpoint in the pseudoautosomal region between DXYS59 and DXYS17. This maps the recessive X-linked form of chondrodysplasia punctata between the proximal boundary of the pseudoautosomal region and DXS31, and an Xp gene controlling growth between DXYS59 and DXS31.     

Ataxia-telangiectasia: an inherited disorder of ionizing-radiation sensitivity in man

Summary This review summarizes the current research on the biochemical defect leading to ataxia-telangiectasia (AT). A DNA repair defect has been linked to AT, although the precise defect has not been found. A critical examination of the evidence for and against a DNA repair defect in AT is presented. Consideration of other recent data on AT raises the possibility that AT may not primarily be the result of a DNA repair defect. Therefore, in this review AT is approached as a syndrome which is defective in the ability to respond to ionizing-radiation-type damage, rather than defective in the ability to repair this damage. However, this does not necessarily exclude the potential involvement of a DNA repair defect in some of the genetically distinct subsets present in AT. Other recent anomalies found in AT, including an altered cell cycle and DNA synthesis profile following ionizing-radiation damage, are also assessed. A suggestion to account for the underlying defect in AT, based on the various research reports, is presented.