PubMed Health⌕ Search

Biomedical subjects

B Fontaine

Publications and source records attributed to B Fontaine.

At least 19 recordsLinked to original sources
PubMed1992

The alpha-subunit of the skeletal muscle sodium channel is encoded proximal to Tk-1 on mouse chromosome 11.

Recent evidence suggests that the human neuromuscular disorders, hyperkalemic periodic paralysis and paramyotonia congenita, are both caused by genetic defects in the alpha-subunit of the adult skeletal muscle sodium channel, which maps near the growth hormone cluster (GH) on Chromosome (Chr) 17q. In view of the extensive homology between this human chromosome and mouse Chr 11, we typed an interspecies backcross to determine whether the murine homolog (Scn4a) of this sodium channel gene mapped within the conserved chromosomal segment. The cytosolic thymidine kinase gene, Tk-1, was also positioned on the genetic map of Chr 11. Both Scn4a and Tk-1 showed clear linkage to mouse Chr 11 loci previously typed in this backcross, yielding the map order: TrJ-(Re, Hox-2, Krt-1)-Scn4a-Tk-1. No mouse mutant that could be considered a model of either hyperkalemic periodic paralysis or paramyotonia congenita has been mapped to the appropriate region of mouse Chr 11. These data incorporate an additional locus into the already considerable degree of homology observed for these human and mouse chromosomes. These data are also consistent with the view that the conserved segment region may extend to the telomere on mouse Chr 11 and on human 17q.

Animals↗
PubMed1992

Attacking today's tuberculosis problem: a multifaceted, coordinated effort.

Tuberculosis is making a comeback in communities across the nation. Increased rates of the disease, particularly with those having HIV/AIDS, have sounded the alarm that quick and decisive action is needed to halt the spread of TB. Multidrug-resistant TB is becoming a primary concern with public health officials. Specific plans and efforts, instigated by the Centers for Disease Control, have outlined the appropriate steps local public health workers, the medical community, and civic and community organizations should take in order to eliminate TB by the year 2010. With the creation of the Task Force on Drug Resistant Tuberculosis, Louisiana has a vehicle with which to combat its growing TB problem.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Loss of chromosome 22 alleles in human sporadic spinal schwannomas.

Acoustic neuromas occur either as sporadic solitary tumors in the general population or as inherited bilateral tumors typically in patients with neurofibromatosis type 2. Loss of heterozygosity for markers on the long arm of chromosome 22 has been reported in both instances, and neurofibromatosis type 2 has been genetically linked to a marker on the long arm of this autosome, suggesting that a unique locus on chromosome 22 is implicated in tumorigenesis of both sporadic and inherited acoustic neuromas. To determine whether the locus for neurofibromatosis type 2 might also be responsible for tumorigenesis of those schwannomas distinct from acoustic neuromas in people without neurofibromatosis type 2, we studied the DNA content of three sporadic spinal schwannomas. In all three, we found loss of heterozygosity for at least three markers on the long arm of chromosome 22, indicating a partial or total monosomy 22 in the tumor. Our results suggest that a locus on chromosome 22 is responsible for tumorigenesis in schwann cells regardless of their location in the central nervous system, and that some other mechanism (genetic or nongenetic) might account for the relative high proportion of schwannomas developing from the eighth cranial nerve.

Adult↗
PubMed1991

Parental origin of chromosome 22 loss in sporadic and NF2 neuromas.

It has recently been proposed that the maternally derived chromosome might be preferentially lost in nonfamilial cases of embryonal or early onset malignant tumors. This observation pointed to a potential role of the parental imprinting of the genome during gametogenesis which would be at least partly maintained in the somatic cells. Neuromas are benign tumors that develop from Schwann cells. They occur either sporadically or in individuals that have a genetic predisposition due to neurofibromatosis type 2 (NF2) and usually are multiple. Regardless of the context of occurrence, in approximately 40% of the investigated cases a loss of a chromosome 22 has been documented either by karyotype analysis or by monitoring somatic loss of heterozygosity. We have now examined the parental origin of the chromosome 22 lost in 19 cases of neuromas of patients with unaffected parents among which 11 were non-NF2 patients (sporadic and unique neuroma) and 8 were NF2 patients (bilateral acoustic or multiple neuromas). In both sets of tumors, the lost chromosome 22 can be of either parental origin. A close to threefold preference for the loss of the maternally derived chromosome was observed and should be either confirmed or disproved by studying a larger number of patients.

Adult↗
PubMed1991

Different gene loci for hyperkalemic and hypokalemic periodic paralysis.

The periodic paralyses are dominantly inherited disorders in which patients acutely develop muscle weakness in association with changes in the level of blood potassium. We recently reported genetic linkage of hyperkalemic periodic paralysis (HIKPP) to the gene encoding the adult form of the skeletal muscle sodium channel on the long arm of chromosome 17. In this paper, we exclude genetic linkage between hypokalemic periodic paralysis (HOKPP) and this sodium channel gene, demonstrating that there is non-allelic genetic heterogeneity among different forms of periodic paralysis. Electrophysiological abnormalities in muscle sodium conductance have been reported for both HIKPP and HOKPP as well as other muscle disorders characterized by membrane hyperexcitability or myotonia (myotonia congenita, paramyotonia congenita and the Schwartz-Jampel syndrome). The possibility that there may be a family of human muscle diseases arising from mutations in the sodium channel suggests these disorders may be classified by categories of mutations within this critical voltage-sensitive membrane protein.

Chromosome Mapping↗
PubMed1991

Molecular genetics of neurofibromatosis 2 and related tumors (acoustic neuroma and meningioma).

Meningioma and acoustic neuroma are among the most frequent primary tumors of the central nervous system. They usually arise as sporadic and solitary tumors. They also develop as multiple tumors in the autosomal dominant genetic disorder neurofibromatosis 2 (NF2). Molecular analysis of meningioma and acoustic neuroma revealed that loss of chromosome 22 alleles was the most frequent genetic alteration found in either sporadic or inherited cases. Subsequent studies showed that a marker in the middle of the long arm of chromosome 22 was linked to the disease in NF2 pedigrees. In this paper, the most recent findings concerning the genetics of NF2 and related tumors are reviewed, and strategy to isolate and characterize the NF2 gene is presented.

Chromosome Mapping↗
PubMed1990

Hyperkalemic periodic paralysis and the adult muscle sodium channel alpha-subunit gene.

Hyperkalemic periodic paralysis (HYPP) is an autosomal dominant disorder characterized by episodes of muscle weakness due to depolarization of the muscle cell membrane associated with elevated serum potassium. Electrophysiological studies have implicated the adult muscle sodium channel. Here, portions of the adult muscle sodium channel alpha-subunit gene were cloned and mapped near the human growth hormone locus (GH1) on chromosome 17. In a large pedigree displaying HYPP with myotonia, these two loci showed tight linkage to the genetic defect with no recombinants detected. Thus, it is likely that the sodium channel alpha-subunit gene contains the HYPP mutation.

Adult↗