Search PubMed⌕ Search

Biomedical subjects

M Zatz

Publications and source records attributed to M Zatz.

At least 91 records · Page 5Linked to original sources
PubMed1997

Deficiency of alpha-actinin-3 (ACTN3) occurs in different forms of muscular dystrophy.

The alpha-actinins belong to a superfamily of cytoskeletal proteins, and their role in human genetic diseases is still unclear. Therefore, they could be good candidates for muscular dystrophies of unknown etiology. We have analyzed alpha-actinin-3 (ACTN3) in muscle biopsies from a total of 54 patients. A complete deficiency was found in 9 patients: 2/12 with classical merosin-positive congenital MD (CMD), 1/12 with Severe Childhood Autosomal Recessive MD (DLMD), but with a positive IF pattern for the proteins of the sarcoglycan complex: 3/14 with mild limb-girdie MD (1LGMD2A and 2 yet unclassified), 1/10 with sarcoglycanopathies (LGMD2C), and 2/6 with Xp21 Duchenne MD (DMD). Patients within the same family, and with the same disease (DMD, LGMD2A, LGMD2C), were discordant for ACTN3 deficiency. Additionally, no correlation was found with the degree of muscle degeneration, nor with the clinical course. One ACTN3-deficient CMD patient showed no mRNA expression for the muscle ACTN3 gene, but the other ACTN3-deficient patients with different forms of muscular dystrophy showed very low or no mRNA expression as well. These results show that the deficiency of ACTN3 is a secondary effect in these dystrophies.

Actinin↗
PubMed1997

The seventh form of autosomal recessive limb-girdle muscular dystrophy is mapped to 17q11-12.

The group of autosomal recessive (AR) muscular dystrophies includes, among others, two main clinical entities, the limb-girdle muscular dystrophies (LGMDs) and the distal muscular dystrophies. The former are characterized mainly by muscle wasting of the upper and lower limbs, with a wide range of clinical severity. This clinical heterogeneity has been demonstrated at the molecular level, since the genes for six AR forms have been cloned and/or have been mapped to 15q15.1 (LGMD2A), 2p12-16 (LGMD2B), 13q12 (LGMD2C), 17q12-q21.33 (LGMD2D),4q12 (LGMD2E), and 5q33-34 (LGMD2F). The AR distal muscular dystrophies originally included two subgroups, Miyoshi myopathy, characterized mainly by extremely elevated serum creatine kinase (CK) activity and by a dystrophic muscle pattern, and Nonaka myopathy, which is distinct from the others because of the normal to slightly elevated serum CK levels and a myopathic muscle pattern with rimmed vacuoles. With regard to our unclassified AR LGMD families, analysis of the affected sibs from one of them (family LG61) revealed some clinical and laboratory findings (early involvement of the distal muscles, mildly elevated serum CK levels, and rimmed vacuoles in muscle biopsies) that usually are not observed in the analysis of patients with LGMD2A-LGMD2F. In the present investigation, through a genomewide search in family LG61, we demonstrated linkage of the allele causing this form of muscular dystrophy to a 3-cM region on 17q11-12. We suggest that this form, which, interestingly, clinically resembles AR Kugelberg-Welander disease, should be classified as LGMD2G. In addition, our results indicate the existence of still another locus causing severe LGMD.

Alleles↗
PubMed1997

The melatonin rhythm-generating enzyme: molecular regulation of serotonin N-acetyltransferase in the pineal gland.

A remarkably constant feature of vertebrate physiology is a daily rhythm of melatonin in the circulation, which serves as the hormonal signal of the daily light/dark cycle: melatonin levels are always elevated at night. The biochemical basis of this hormonal rhythm is one of the enzymes involved in melatonin synthesis in the pineal gland-the melatonin rhythm-generating enzyme-serotonin N-acetyltransferase (arylalkylamine N-acetyltransferase, AA-NAT, E.C. 2.3.1.87). In all vertebrates, enzyme activity is high at night. This reflects the influences of internal circadian clocks and of light. The dynamics of this enzyme are remarkable. The magnitude of the nocturnal increase in enzyme activity ranges from 7- to 150-fold on a species-to-species basis among vertebrates. In all cases the nocturnal levels of AA-NAT activity decrease very rapidly following exposure to light. A major advance in the study of the molecular basis of these changes was the cloning of cDNA encoding the enzyme. This has resulted in rapid progress in our understanding of the biology and structure of AA-NAT and how it is regulated. Several constant features of this enzyme have become apparent, including structural features, tissue distribution, and a close association of enzyme activity and protein. However, some remarkable differences among species in the molecular mechanisms involved in regulating the enzyme have been discovered. In sheep, AA-NAT mRNA levels show relatively little change over a 24-hour period and changes in AA-NAT activity are primarily regulated at the protein level. In the rat, AA-NAT is also regulated at a protein level; however, in addition, AA-NAT mRNA levels exhibit a 150-fold rhythm, which reflects cyclic AMP-dependent regulation of expression of the AA-NAT gene. In the chicken, cyclic AMP acts primarily at the protein level and a rhythm in AA-NAT mRNA is driven by a noncyclic AMP-dependent mechanism linked to the clock within the pineal gland. Finally, in the trout, AA-NAT mRNA levels show little change and activity is regulated by light acting directly on the pineal gland. The variety of mechanisms that have evolved among vertebrates to achieve the same goal-a rhythm in melatonin-underlines the important role melatonin plays as the hormonal signal of environmental lighting in vertebrates.

Amino Acid Sequence↗
PubMed1996

Linkage studies in bipolar affective disorder with markers on chromosome 21.

Straub et al. (1994: Nature Genet. 8. 291-296) have suggested that a susceptibility gene for bipolar affective disorder is located at chromosome 21q22.3, on the basis of linkage analysis in one large family. This result has been supported by Gurling et al. (1995: Nature Genet. 10, 8-9) who also found some evidence for linkage to this region under locus heterogeneity. In order to investigate the validity of these results and to estimate how broadly applicable they are, we performed a linkage study between bipolar affective disorder and two DNA markers (D21S171 and PFKL) from 21q22.3 using 60 bipolar pedigrees from three European centres and Brazil. The most positive result obtained was a maximised admixture lod score of 1.2 for the marker PFKI, under the assumption of locus heterogeneity, dominant transmission and a diagnostic classification which included recurrent unipolar depression. However, since lod scores obtained for both markers were substantially negative overall, we conclude that there is no common major gene for bipolar affective disorder at 21q22.3. It remains possible that a gene of major effect in this region operates in a minority of families.

Bipolar Disorder↗
PubMed1996

Tryptophan hydroxylase mRNA levels are regulated by the circadian clock, temperature, and cAMP in chick pineal cells.

Chick pineal cells contain a circadian oscillator that derives rhythmic synthesis and secretion of melatonin even in dispersed cell culture. Here, we demonstrate that the mRNA encoding tryptophan hydroxylase (TPH), the first enzyme in the melatonin synthetic pathway, is expressed rhythmically under the control of the circadian clock. TPH message levels doubled between early day and early night, under both cyclic lightning and constant lightning conditions. The amplitude of the TPH mRNA rhythm was increased to 4-fold by culturing the cells at 43.3 degrees C for 48 h instead of 36.7 degrees C. Addition of forskolin to the cultures in early day produced a modest increase (50%) in TPH message levels but had no effect at other times. Because TPH mRNA are regulated by the endogenous pineal circadian clock, this provides a valuable system in which the molecular mechanism of clock control of gene expression.

Animals↗
PubMed1996

Genetic and physical mapping at the limb-girdle muscular dystrophy locus (LGMD2B) on chromosome 2p.

The limb-girdle muscular dystrophies (LGMD) are a genetically heterogeneous group of disorders, different forms of which have been mapped to at least six distinct genetic loci. We have mapped an autosomal recessive form of LGMD (LGMD2B) to chromosome 2p13. Two other conditions have been shown to map to this region or to the homologous region in mouse: a gene for a form of autosomal recessive distal muscular dystrophy, Miyoshi myopathy, shows linkage to the same markers on chromosome 2p as LGMD2B, and an autosomal recessive mouse mutation mnd2, in which there is rapidly progressive paralysis and muscle atrophy, has been mapped to mouse chromosome 6 to a region showing conserved synteny with human chromosome 2p12-p13. We have assembled a 6-cM YAC contig spanning the LGMD2B locus and have mapped seven genes and 13 anonymous polymorphic microsatellites to it. Using haplotype analysis in the linked families, we have narrowed our region of interest to a 0-cM interval between D2S2113 and D2S2112/D2S145, which does not overlap with the critical region for mnd2 in mouse. Use of these most closely linked markers will help to determine the relationship between LGMD2B and Miyoshi myopathy. YACs selected from our contig will be the starting point for the cloning of the LGMD2B gene and thereby establish the biological basis for this form of muscular dystrophy and its relationship with the other limb-girdle muscular dystrophies.

Animals↗
PubMed1996

The phenotype of chromosome 2p-linked limb-girdle muscular dystrophy.

This study reports on a detailed clinical, electrophysiological, muscle computed tomography (CT) and laboratory investigation carried out on five families with definite linkage to chromosome 2p. Some clinical and laboratory features were common to most of the patients, such as the very high serum creatine kinase (CK) levels (mean 43.70 times the normal). The onset was most frequently in the late teens or early twenties with weakness and wasting of the pelvic girdle muscles. All patients had normal motor milestones and had not complained of any symptoms of muscle disease in early childhood. The clinical course was variable both between and within some families, but was most often slowly progressive. Some variability in the pattern of muscle involvement between the different families has also been observed.

Adolescent↗
PubMed1996

Autosomal recessive limb-girdle muscular dystrophy, LGMD2F, is caused by a mutation in the delta-sarcoglycan gene.

Limb-girdle muscular dystrophies (LGMD) are a heterogeneous group of inherited neuromuscular disorders characterized by proximal muscular weakness of the pelvic and shoulder girdles and a variable progression with symptoms, ranging from very severe to mild. One autosomal dominant (LGMD1A, at chromosome 5q22.3-31.3) (ref. 3) and five autosomal recessive (AR) loci responsible for this phenotype have been identified: LGMD2A at 15q (ref. 4); LGMD2B at 2p (ref. 5), LGMD2C at 13q (ref. 6), LGMD2D at 17q (ref. 7) and LGMD2E at 4q (refs 8,9). In the muscle membrane, dystrophin associates with several proteins and glycoproteins organized in two main subcomplexes: the dystroglycan (DG) and sarcoglycan (SG) complexes. The genes for LGMD2C, LGMD2D and LGMD2E code for proteins of the SG complex. We recently mapped a sixth AR form of LGMD, LGMD2F, to chromosome 5q33-34 in two Brazilian families. In the same chromosomal interval we also mapped the delta SG gene, encoding a novel 35-kD component of the sarcoglycan (SG) complex. We now show that a homozygous mutation in the delta SG gene (a single nucleotide deletion that alters its reading frame) is the cause of LGMD2F.

Adolescent↗
PubMed1996

Genomic screening for beta-sarcoglycan gene mutations: missense mutations may cause severe limb-girdle muscular dystrophy type 2E (LGMD 2E).

Autosomal recessive limb-girdle muscular dystrophies (LGMDs) are genetically heterogeneous. A subgroup of these disorders is caused by mutations in the dystrophin-associated sarcoglycan complex. Truncating mutations in the 43 kDa beta-sarcoglycan gene (LGMD 2E) were originally identified in a sporadic case of Duchenne-like muscular dystrophy, and a common missense mutation (T151R) was identified independently in Indiana Amish pedigrees with a milder form of LGMD. To facilitate mutational analysis of larger numbers of patients directly from genomic DNA, as opposed to reverse transcribed RNA from muscle biopsies, we have determined the genomic structure of the beta-sarcoglycan gene. The open reading frame of the beta-sarcoglycan coding region extends over six exons. Primers were designed for PCR amplification of single exons from genomic DNA and subsequent single strand conformation polymorphism (SSCP) analysis. We screened 15 patients from the Brazilian LGMD patient population, 13 of whom followed a severe course. Most of the patients had been assessed previously for deficiency of alpha-sarcoglycan immunofluorescence on muscle biopsy sections as a marker for disease of the sarcoglycan complex. Novel mutations in two familial and two sporadic cases of severe childhood-onset LGMD were identified. Only one of these patients carried a truncating mutation (homozygous 2 bp deletion, FS164TER), while the other three carried missense mutations (homozygous R91P, homozygous M100K, heterozygous recessive L108R; only one allele could be identified in this family). All three missense mutations occurred in exon 3, coding for the immediate extracellular domain. Complete absence for all three of the known sarcoglycans was noted by immunohistochemistry on muscle biopsy sections of the patients.

Amino Acid Sequence↗
PubMed1996

The sarcoglycan complex in the six autosomal recessive limb-girdle muscular dystrophies.

To enhance our understanding of the autosomal recessive limb-girdle muscular dystrophy (LGMD), patients from six genetically distinct forms (LGMD2A to LGMD2F) were studied with antibodies directed against four sarcoglycan subunits (alpha-, beta-, gamma-, delta-SG), dystrophin, beta-dystroglycan (beta-DG) and merosin. All patients with LGMD2A and 2B had a mild clinical course while those with a primary sarcoglycan mutation (LGMD2C to 2F) had a range of clinical severity. Dystrophin and merosin immunofluorescence pattern was positive in patients with all six AR LGMDs. The majority of patients with a severe Duchenne-like phenotype presented total absence of the SG complex. However, some exceptions were found in 13q linked patients, indicating that the presence of a certain labelling for components of the SG may not be prognostic for a milder phenotype. The observation that the primary absence of alpha-SG results in the total absence of beta- and delta-SG but not of gamma-SG suggests that the alpha-, beta- and delta-subunits of sarcoglycan may be more closely associated. A secondary reduction in dystrophin amount was seen in patients with primary sarcoglycan mutations, which was most marked in patients with primary beta-, gamma- and delta-SG deficiencies. In contrast, beta-DG staining was retained in all patients, suggesting that the association between SG and DG subcomplexes is not so strong. Based on the above findings, we have refined the model for the interaction among the known glycoproteins of the sarcoglycan complex, within the DGC.

Adolescent↗
PubMed1996

Linkage analysis in autosomal recessive limb-girdle muscular dystrophy (AR LGMD) maps a sixth form to 5q33-34 (LGMD2F) and indicates that there is at least one more subtype of AR LGMD.

Limb-girdle muscular dystrophies (LGMDs) represent a clinically heterogeneous group of genetic diseases characterised by progressive weakness of the pelvic and shoulder girdle muscles. An autosomal dominant form (LGMD1A) has been mapped at 5q22.3-31.3, while five genes responsible for the autosomal recessive forms were mapped respectively at: 15q15.1 (LGMD2A), 2p12-p16 (LGMD2B), 13q12 (LGMD2C), 17q12-q21.33 (LGMD2D) and 4q12 (LGMD2E). Among 17 autosomal recessive (AR) LGMD Brazilian families with at least three affected sibs, we were able to exclude four families (one mild and three severe) from all these five known loci as well as from the dystroglycan and syntrophin genes. Therefore, we have performed a genome-wide search in two of the severely affected families, which are alpha-sarcoglycan negative. We demonstrate linkage of these two Duchenne muscular dystrophy-like families to 5q33-34, and propose to classify them as LGMD2F. In addition, linkage analysis in the other two genealogies that are alpha-sarcoglycan positive suggests that there is at least one other gene which causes AR LGMD.

Chromosome Mapping↗
PubMed1996

A gene which causes severe ocular alterations and occipital encephalocele (Knobloch syndrome) is mapped to 21q22.3.

Knobloch syndrome (KS), characterized by high myopia, vitreoretinal degeneration with retinal detachment, macular abnormalities and occipital encephalocele, was recently confirmed as autosomal recessive. Here we report the assignment of the gene for this syndrome to 21q22.3 with the marker D21S171 through homozygosity mapping in a highly inbred Brazilian family with 11 affected individuals. A total of nine markers spanning a region of 15.2 cM of the chromosome 21q22.3 were tested and the candidate region was restricted to an interval of 4.3 cM.

Abnormalities, Multiple↗
PubMed1996

Main clinical features of the three mapped autosomal recessive limb-girdle muscular dystrophies and estimated proportion of each form in 13 Brazilian families.

Autosomal recessive limb-girdle muscular dystrophies (AR LGMD) represent a group of muscle diseases with a wide spectrum of clinical signs, varying from very severe to mild. Four different loci that when mutated cause the AR LGMD phenotype have been mapped or cloned or both: in two of them the linked families seem to have a relatively mild phenotype (LGMD2a and LGMD2b), in the third one the reported linked families show a more severe clinical course (LGMD2c), while mutations in the fourth locus may cause severe or mild phenotypes (LGMD2d). The relative proportion of each of these genetic forms among the LGMD families and whether there are other genes that when mutated cause this phenotype is unknown. The closest available informative markers for each of the mapped AR LGMD genes have been tested in 13 Brazilian families with at least three affected patients. The findings from the present report confirm non-allelic heterogeneity for LGMD and suggest that in our population about 33% of the LGMD families are caused by mutations in the 15q gene, 33% in the 2p gene, 17% by mutations in the adhalin gene, and less than 10% may be by mutations at the 13q locus. They also suggest that there is at least one other gene responsible for this phenotype. In addition, the main clinical features of the different forms are discussed.

Adolescent↗
PubMed1996

Mild and severe muscular dystrophy caused by a single gamma-sarcoglycan mutation.

Autosomal recessive muscular dystrophy is genetically heterogeneous. One form of this disorder, limb-girdle muscular dystrophy type 2C (LGMD 2C), is prevalent in northern Africa and has been shown to be associated with a single mutation in the gene encoding the dystrophin-associated protein gamma-sarcoglycan. The previous mutation analysis of gamma-sarcoglycan required the availability of muscle biopsies. To establish a mutation assay for genomic DNA, the intron-exon structure of the gamma-sarcoglycan gene was determined, and primers were designed to amplify each of the exons encoding gamma-sarcoglycan. We studied a group of Brazilian muscular dystrophy patients for mutations in the gamma-sarcoglycan gene. These patients were selected on the basis of autosomal inheritance and/or the presence of normal dystrophin and/or deficiency of alpha-sarcoglycan immunostaining. Four of 19 patients surveyed had a single, homozygous mutation in the gamma-sarcoglycan gene. The mutation identified in these patients, all of African-Brazilian descent, is identical to that seen in the North African population, suggesting that even patients of remote African descent may carry this mutation. The phenotype in these patients varied considerably. Of four families with an identical mutation, three have a severe Duchenne-like muscular dystrophy. However, one family has much milder symptoms, suggesting that other loci may be present that modify the severity of the clinical course resulting from gamma-sarcoglycan gene mutations.

Adolescent↗