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Biomedical subjects

L Yamaoka

Publications and source records attributed to L Yamaoka.

15 recordsLinked to original sources
PubMed1997

Confirmation of linkage of oculopharyngeal muscular dystrophy to chromosome 14q11.2-q13 in American families suggests the existence of a second causal mutation.

Oculopharyngeal muscular dystrophy (OPMD) is a late-onset, autosomal dominant disorder characterized by progressive ptosis, dysphagia, and extremity weakness. Linkage of OPMD to 14q11.2-q13 has been reported in a series of French-Canadian families. Tightly linked markers have been defined and haplotype analysis in these data show a single segregating disease chromosome throughout the OPMD French-Canadian families. We have ascertained and sampled five multigenerational outbred American OPMD families. Four of the five families have known French-Canadian ancestry while the fifth is of English/Scottish origin. Linkage analysis was performed using standard likelihood methods. A peak multipoint lod score of 6.30 was obtained for the marker MYH7.1 in the OPMD families. The English/ Scottish family exhibited a different chromosomal haplotype for the OPMD alleles than the families of French-Canadian origin. These data suggest this family may represent a second, possibly independent mutation in this disorder. Linkage was confirmed to chromosome 14q11.2-q13 with no evidence of genetic heterogeneity.

Adult↗
PubMed1996

No association between alpha 1-antichymotrypsin and familial Alzheimer's disease.

Alzheimer's disease (AD) is the most common mid to late age-of-onset neurodegenerative disorder. AD has a strong and complex genetic etiology, and multiple genes, acting independently and/or interacting, likely affect the risk of developing AD. Several genes involved with AD already have been described, but only the APOE gene on chromosome 19q has been shown to affect the risk of the most common form of AD, occurring with onset over the age of 65. Because a substantial portion of late-onset AD is not explained by APOE, other genes affecting late-onset AD likely occur. These could act either independently or perhaps interact with APOE. alpha 1-Antichymotrypsin (ACT) is a major component of the amyloid plaques found in the brains of AD patients and may play a role in the pathophysiology of AD. It has been proposed that a specific polymorphism within the ACT gene interacts with APOE to increase the risk of developing AD. Our results do not confirm this finding.

Adult↗
PubMed1996

No genetic effect of alpha1-antichymotrypsin in Alzheimer disease.

Alzheimer disease (AD) is the most common neurodegenerative disorder for individuals over the age of 40. AD has a complex etiology, and it is likely that multiple genes, acting independently and/or interacting, affect the risk of developing AD. Several genes involved with AD have been described already, but only the APOE gene on chromosome 19q has been shown to affect the risk of the common late onset form of AD. alpha1-Antichymotrypsin (AACT) is a major component of the amyloid plaques found in the brains of AD patients, and an allele in its gene has been proposed to increase the risk of developing AD when also associated with the APOE-4 allele. We have examined the role of this AACT polymorphism in a large set of families and sporadic cases, and do not see any effect, either alone or in combination with the APOE-4 allele.

Alzheimer Disease↗
PubMed1996

Confirmation of linkage of oculopharyngeal muscular dystrophy to chromosome 14q11.2-q13.

Oculopharyngeal muscular dystrophy is a late-onset, autosomally dominant disorder characterized by progressive ptosis, dysphagia, and extremity weakness. Linkage of oculopharyngeal muscular dystrophy to 14q11.2-q13 has been reported in a series of French Canadian families. Haplotype analysis in these data shows a single segregating disease chromosome, suggesting a founder effect in this population. We ascertained and sampled for linkage studies 5 multigenerational American families with oculopharyngeal muscular dystrophy. Four of the 5 families have known French Canadian ancestry while the fifth is of English/Scottish origin. A peak multipoint lod score of 6.30 was obtained for the marker MYH7.1 in the families, confirming linkage to 14q11.2-q13. The English/Scottish family exhibited a different chromosomal haplotype for the oculopharyngeal muscular dystrophy alleles than did the families of French Canadian origin. These data suggest that this family may represent a second, possibly independent mutation in this disorder.

Age of Onset↗
PubMed1990

Presymptomatic and prenatal diagnosis in myotonic dystrophy by genetic linkage studies.

Myotonic dystrophy (DM) is an autosomal dominant disorder with age-dependent penetrance and extremely variable expressivity. With the genetic markers CKMM and ApoC2, both of which are tightly linked and centromeric to DM, presymptomatic and prenatal diagnosis for myotonic dystrophy is available. We present the results of 4 families tested for carrier status of myotonic dystrophy by genetic linkage studies and define potential limitations of these studies. A protocol for genetic linkage studies in DM is outlined.

Adult↗
PubMed1988

Systematic gene mapping in man: data management considerations.

The application of recombinant DNA technology to linkage analysis is revolutionizing the gene mapping field through the availability of an increasing number of restriction fragment length polymorphisms (RFLP). The successful mapping of the human genome will lead to a new era of research in human genetics with implications for carrier detection and prenatal diagnosis in any number of disorders. In addition, the development of RFLP tightly linked to a disease is critical for the potential identification of the genetic defect. A systematic approach to human gene mapping whereby it is possible to simultaneously screen several disorders for linkage is discussed. Guidelines for the database management, field studies, DNA and lymphoblast cell transformation, family history and laboratory data are included. This methodology represents the integration and application of statistical and molecular genetic, clinical and tissue culture expertise to human gene mapping.

Chromosome Aberrations↗
PubMed1988

Update on the molecular genetics of Duchenne muscular dystrophy.

Three separate lines of evidence led to the assignment of the Duchenne muscular dystrophy (DMD) gene to the 21.2 band on the short arm of the X chromosome. A portion of the putative gene, thought to extend over 1-2 million base pairs has been recently cloned. DNA probes from the Xp21.2 region detect large deletions in 5-20% DMD boys and are presumed to lead to the DMD phenotype in those individuals. Deletions have also been noted in the DNA of patients with Becker muscular dystrophy. These exciting developments have a direct bearing on carrier detection and prenatal diagnosis. Prenatal diagnosis in deletion families approaches greater than 99% accuracy and can be utilized to save 50% of normal male fetuses carried by carrier mothers who would otherwise choose to abort all male fetuses.

Cloning, Molecular↗
PubMed1987

A new probe for the diagnosis of myotonic muscular dystrophy.

Myotonic muscular dystrophy (DM) is the most common muscular dystrophy, affecting adults as well as children. It is inherited as an autosomal dominant trait and is characterized by variable expressivity and late age-of-onset. Linkage studies have established the locus on chromosome 19. In order to identify tightly linked probes for diagnosis as well as to define in detail the DM gene region, chromosome 19 libraries were constructed and screened for restriction fragment length polymorphisms tightly linked to DM. A genomic clone, LDR152 (D19S19), was isolated that is tightly linked to DM; recombination fraction = 0.0 (95% confidence limits 0.0-0.03); lod score, 15.4.

Adult↗
PubMed1987

Familial inheritance of a DXS164 deletion mutation from a heterozygous female.

Restriction-fragment-length-polymorphism analysis was used to examine a female who is segregating for Duchenne muscular dystrophy (DMD) and a deletion of the DXS164 region of the X chromosome. The segregating female has no prior family history of DMD, and she has two copies of the DXS164 region in her peripheral blood lymphocytes. The following two hypotheses are proposed to explain the coincidence of the DMD phenotype and deletion of the DXS164 region in her offspring: (1) she may be a gonadal mosaic for cells with two normal X chromosomes and cells with one normal X chromosome and an X chromosome with a deletion of the DXS164 region; and (2) she may carry a familial X;autosome translocation in which the DXS164 region is deleted from one X chromosome and translocated to an autosome. The segregation of DMD and the DXS164 deletion in this family illustrates the importance of extended pedigree analysis when DXS164 deletions are used to identify female carriers of the DMD gene.

Chromosome Deletion↗