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Biomedical subjects

W Y Hung

Publications and source records attributed to W Y Hung.

At least 37 records · Page 2Linked to original sources
PubMed1994

Linkage of recessive familial amyotrophic lateral sclerosis to chromosome 2q33-q35.

Amyotrophic lateral sclerosis (ALS) usually presents as a sporadic disorder of motor neurons. However, familial forms of ALS have been described--autosomal dominant forms (ALS1, ALS3), clinically indistinguishable from the sporadic form, and autosomal recessive forms with early onset and slower progression of symptoms (ALS2). To localize the gene for one of the autosomal recessive forms of ALS, we applied linkage analysis to a large inbred family from Tunisia. A lod score maximum of Zmax = 8.2 at theta = 0.00 was obtained with marker D2S72 located on chromosome 2q33-q35. The fine mapping of this region suggested that the ALS2 locus lies in the 8 cM segment flanked by D2S155 and D2S115.

Adolescent↗
PubMed1994

Linkage of a locus for autosomal dominant familial spastic paraplegia to chromosome 2p markers.

'Pure' autosomal dominant familial spastic paraplegia (SPG) is a neurodegenerative disease which clinically manifests as spasticity of the lower limbs. Dominantly inherited SPG is known to be clinically heterogenous and has been classified into late-onset and early-onset types, based on the age of onset of symptoms. We tested five autosomal dominant SPG families for genetic linkage and established linkage to chromogene 2p markers (Z(theta) = 3.65) with evidence of genetic locus heterogeneity. Three late-onset SPG families and one early-onset SPG family had high posterior probability of linkage (P > 0.94) to chromosome 2p, while the fifth family (a very early-onset family) was not linked to chromosome 2 and showed high probability of linkage to chromosome 14q. These data provide a basis for a classification of SPG according to chromosome location rather than age of onset of symptoms.

Chromosome Mapping↗
PubMed1994

Linkage of 'pure' autosomal recessive familial spastic paraplegia to chromosome 8 markers and evidence of genetic locus heterogeneity.

'Pure' familial spastic paraplegias (FSP) are neurodegenerative disorders that are clinically characterized by progressive spasticity of the lower limbs and are inherited as autosomal dominant (DFSP) or autosomal recessive (RFSP) traits. The primary defect in FSP is unknown. Genetic linkage analysis was applied to five RFSP families from Tunisia. In four of these five families tight linkage of the RFSP locus was established to the chromosome 8 markers, D8S260, D8S166, D8S285, PLAT, and D8S279. The RFSP locus in the fifth family was not linked to these markers which provided evidence of genetic locus heterogeneity in RFSP. Identification of the RFSP gene on chromosome 8 will help in understanding the genetic factors in motor neuron degeneration.

Adolescent↗
PubMed1993

Amyotrophic lateral sclerosis and structural defects in Cu,Zn superoxide dismutase.

Single-site mutants in the Cu,Zn superoxide dismutase (SOD) gene (SOD1) occur in patients with the fatal neurodegenerative disorder familial amyotrophic lateral sclerosis (FALS). Complete screening of the SOD1 coding region revealed that the mutation Ala4 to Val in exon 1 was the most frequent one; mutations were identified in exons 2, 4, and 5 but not in the active site region formed by exon 3. The 2.4 A crystal structure of human SOD, along with two other SOD structures, established that all 12 observed FALS mutant sites alter conserved interactions critical to the beta-barrel fold and dimer contact, rather than catalysis. Red cells from heterozygotes had less than 50 percent normal SOD activity, consistent with a structurally defective SOD dimer. Thus, defective SOD is linked to motor neuron death and carries implications for understanding and possible treatment of FALS.

Amino Acid Sequence↗
PubMed1993

Notexin-induced muscle injury in the dog.

Notexin, a myotoxic phospholipase, was used to induce focal necrosis in the sartorius muscles of normal mixed-breed adult dogs and in 12-week-old beagles. Notexin injury caused pathologic changes similar to those of Duchenne muscular dystrophy (DMD) and its canine homologue, golden retriever muscular dystrophy (GRMD). All three conditions are characterized by increased serum creatine kinase (CK) levels, sarcolemmal defects, delta lesions, hyaline degeneration of myofibers, calcium-positive myofibers, and minimal effects on neurovascular structures. Four and 24 h after exposure to notexin, serum CK levels were elevated, and many myofibers were necrotic. In addition, by 24 h the necrotic areas were heavily invaded by mononuclear cells, and calcium-positive myofibers were prominent. Capillaries appeared intact even in areas of marked myonecrosis. Massive cellular infiltrate and myotube formation was evident at 3 days post injury. By 7 days, most affected fascicles were occupied by small immature myofibers. Regeneration was largely complete at 21 days. Our results suggest that notexin-induced muscle injury in dogs will be useful in the evaluation of potential therapies for DMD such as myoblast transplantation.

Animals↗
PubMed1992

An error in dystrophin mRNA processing in golden retriever muscular dystrophy, an animal homologue of Duchenne muscular dystrophy.

Golden retriever muscular dystrophy (GRMD) is a spontaneous, X-linked, progressively fatal disease of dogs and is also a homologue of Duchenne muscular dystrophy (DMD). Two-thirds of DMD patients carry detectable deletions in their dystrophin gene. The defect underlying the remaining one-third of DMD patients is undetermined. Analysis of the canine dystrophin gene in normal and GRMD dogs has failed to demonstrate any detectable loss of exons. Here, we have demonstrated a RNA processing error in GRMD that results from a single base change in the 3' consensus splice site of intron 6. The seventh exon is then skipped, which predicts a termination of the dystrophin reading frame within its N-terminal domain in exon 8. This is the first example of dystrophin deficiency caused by a splice-site mutation.

Amino Acid Sequence↗
PubMed1991

Linkage of a gene causing familial amyotrophic lateral sclerosis to chromosome 21 and evidence of genetic-locus heterogeneity.

BACKGROUND: Amyotrophic lateral sclerosis is a progressive neurologic disorder that commonly results in paralysis and death. Despite more than a century of research, no cause of, cure for, or means of preventing this disorder has been found. In a minority of cases, it is familial and inherited as an autosomal dominant trait with age-dependent penetrance. In contrast to the sporadic form of amyotrophic lateral sclerosis, the familial form provides the opportunity to use molecular genetic techniques to localize an inherited defect. Furthermore, such studies have the potential to discover the basic molecular defect causing motor-neuron degeneration. METHODS AND RESULTS: We evaluated 23 families with familial amyotrophic lateral sclerosis for linkage of the gene causing this disease to four DNA markers on the long arm of chromosome 21. Multipoint linkage analyses demonstrated linkage between the gene and these markers. The maximum lod score--5.03--was obtained 10 centimorgans distal (telomeric) to the DNA marker D21S58. There was a significant probability (P less than 0.0001) of genetic-locus heterogeneity in the families. CONCLUSIONS: The localization of a gene causing familial amyotrophic lateral sclerosis provides a means of isolating this gene and studying its function. Insight gained from understanding the function of this gene may be applicable to the design of rational therapy for both the familial and sporadic forms of the disease.

Adolescent↗
PubMed1991

Genetic linkage analysis of nerve growth factor (beta) in familial Alzheimer's disease.

Recent studies have not shown linkage of late-onset (mean age, greater than 60 years) familial Alzheimer's disease (FAD) to the chromosome 21 locus reported linked to early-onset FAD. Beta nerve growth factor (beta-NGF) has been considered a candidate gene in the pathogenesis and therapy of FAD, based on its localization in the cortex and hippocampus and its ability to enhance the growth and survival of cholinergic neurons. A 1.5-kb fragment of the beta-NGF gene was used to detect a BglII restriction fragment length polymorphism, which was then used for linkage analysis. A total of 30 families (27 late onset) with 147 affected members were studied. Close linkage (theta less than or equal to 0.03, z less than or equal to -2.00) of late-onset FAD with beta-NGF was excluded. Two apparent obligate crossovers between affected members were detected in different autopsy-confirmed families. Based on these results, beta-NGF is not the gene responsible for late-onset FAD in the families analyzed.

Aged↗
PubMed1991

Identification of Duchenne muscular dystrophy genomic probe P20 constant Taql fragment corresponding to the EcoRV and Mspl polymorphisms.

The majority of Duchenne and Becker muscular dystrophy cases are caused by deletions observable in Southern blots with cDNA probes for the gene. When the deletion includes polymorphic probes, they may be used to determine carrier status by deletion segregation analysis: non-inheritance of parental alleles, or heterozygosity. The polymorphic genomic probe P20 is deleted in a large percentage of probands. P20 hybridizes with two constant fragments of 6.7 and 0.8 kb in Taql digests. In a number of probands, only the larger P20 Taql fragment is deleted. This study demonstrates that this fragment corresponds with the polymorphic EcoRV and Mspl fragments of P20. Families in which the upper Taql fragment is deleted may be screened for carrier status using non-inheritance of parental alleles or heterozygosity of P20 in EcoRV or Mspl digests.

Blotting, Southern↗
PubMed1991

North Carolina macular dystrophy: exclusion map using RFLPs and microsatellites.

The autosomal dominant macular dystrophies are a confusing group of poorly understood diseases. Linkage studies will greatly aid our classification of these disorders and hopefully provide insight into central retinal function and dysfunction such as occurs in age-related macular degeneration. North Carolina macular dystrophy is one such disease that has been amenable to linkage analysis because of the large pedigree size. Seventy-six polymorphic markers have been tested for linkage and exclusion data are presented.

Chromosome Mapping↗
PubMed1991

Localization of Charcot-Marie-Tooth disease type 1a (CMT1A) to chromosome 17p11.2.

Charcot-Marie-Tooth (CMT) disease type 1a has been previously localized to chromosome 17 using the markers D17S58 and D17S71. In that report we were unable to provide unequivocal localization of the CMT1A gene on either the proximal p or the q arm. Therefore, data from one additional CMT1A family and typing of other probes spanning the pericentromeric region of chromosome 17 (D17S73, D17S58, D17S122, D17S125, D17S124) were analyzed. Multipoint analysis demonstrates convincing evidence (log likelihood difference greater than 5) that the CMT1A gene lies within 17p11.2 and most likely between the flanking markers D17S122 and D17S124.

Charcot-Marie-Tooth Disease↗
PubMed1991

Linkage studies in tuberous sclerosis. Chromosome 9?, 11?, or maybe 14!

Published reports show linkage of tuberous sclerosis (TSC) to either chromosome 9 in some families or chromosome 11 in other families. We studied 243 individuals (82 with TSC) from 16 multigenerational TSC families. The diagnosis of TSC conformed to the criteria of Gomez. Penetrance was estimated at 0.90. DNA markers were analyzed using Southern blotting, probe hybridization, autoradiography, and genetic linkage analysis. Two-point lod scores for TSC were calculated for 43 genetic markers distributed over 11 chromosomes. Tests for homogeneity rejected the null hypothesis of homogeneity. Linkage to TSC was excluded (z less than or equal to -2, theta greater than or equal to 0.05) for 23 of these markers including 9q34 and 11q markers. One family gave z(theta max) = 1.8, theta max = 0.001 with ABO (on 9q34), and two other families attained lod scores greater than 1 for 9q34-region markers. The lod score for TSC versus chromosome 14 marker pAW101 (D14S1) was z(theta max) = 1.98, theta max = 0.15. A single large family has overall negative lod scores for markers localized to both chromosome 9 and chromosome 11. These data confirm genetic heterogeneity in TSC and suggest linkage of some families to 9q34. Furthermore, the data suggest that 14q may be an interesting area.

Chromosome Mapping↗
PubMed1991

Linkage studies in familial Alzheimer disease: evidence for chromosome 19 linkage.

A genetic component in the etiology of Alzheimer disease (AD) has been supported by indirect evidence for several years, with autosomal dominant inheritance with age-dependent penetrance being suggested to explain the familial aggregation of affecteds. St. George Hyslop et al. reported linkage of familial AD (FAD) in four early-onset families (mean age at onset [M] less than 50 years). Subsequent studies have been inconsistent in their results; Goate et al. also reported positive lod scores. However, both Pericak-Vance et al.'s study of a series of mainly late-onset FAD families (M greater than 60 years) and Schellenberg et al.'s study failed to confirm linkage to chromosome 21 (CH21). These various studies suggest the possibility of genetic heterogeneity, with some families linked to CH21 and others unlocalized. Recently, St. George Hyslop et al. extended their analysis to include additional families. The extended analyses supported their earlier finding of linkage to CH21, while showing strong evidence of heterogeneity between early-onset (M less than 65 years) and late-onset (M greater than 60 years) FAD families. Because our families did not show linkage to CH21, we undertook a genomic search for an additional locus for FAD. Because of both the confounding factor of late age at onset of FAD and the lack of clear evidence of Mendelian transmission in some of our families, we employed the affected-pedigree-member (APM) method of linkage analysis as an initial screen for possible linkage. Using this method, we identified two regions suggesting linkage: the proximal long arm of chromosome 19 (CH19) and the CH21 region of FAD linkage reported by St. George Hyslop et al. Application of standard likelihood (LOD score) analysis to these data support the possibility of an FAD gene locate on CH19, particularly in the late-onset FAD families. These data further suggest genetic heterogeneity and delineate this region of CH19 as an area needing additional investigation in FAD.

Age Factors↗
PubMed1990

Isolation and localization of a slow troponin (TnT) gene on chromosome 19 by subtraction hybridization of a cDNA muscle library using myotonic dystrophy muscle cDNA.

Subtraction hybridization techniques were used to isolate 91 cDNA clones which are overexpressed in normal control skeletal muscle relative to muscle from patients with myotonic muscular dystrophy. The gene responsible for myotonic dystrophy (DM) has been localized to the 19q13.2-13.3 region of chromosome 19. To test as a candidate gene for DM, clones which represent differences in transcription are analyzed for localization to chromosome 19. One clone, designated MSL 366, was found to be on the long arm of chromosome 19 distal to the CKMM gene at 19q13.2. Sequence analysis confirmed that MSL 366 is the cDNA for human slow skeletal muscle troponin T. A genomic clone has been isolated and linkage studies with DM are in progress.

Base Sequence↗