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Biomedical subjects

M H Brilliant

Publications and source records attributed to M H Brilliant.

At least 19 recordsLinked to original sources
PubMed1997

Mice devoid of gamma-aminobutyrate type A receptor beta3 subunit have epilepsy, cleft palate, and hypersensitive behavior.

gamma-Aminobutyric acid type A receptors (GABA(A)-Rs) mediate the bulk of rapid inhibitory synaptic transmission in the central nervous system. The beta3 subunit is an essential component of the GABA(A)-R in many brain regions, especially during development, and is implicated in several pathophysiologic processes. We examined mice harboring a beta3 gene inactivated by gene targeting. GABA(A)-R density is approximately halved in brain of beta3-deficient mice, and GABA(A)-R function is severely impaired. Most beta3-deficient mice die as neonates; some neonatal mortality, but not all, is accompanied by cleft palate. beta3-deficient mice that survive are runted until weaning but achieve normal body size by adulthood, although with reduced life span. These mice are fertile but mothers fail to nurture offspring. Brain morphology is grossly normal, but a number of behaviors are abnormal, consistent with the widespread location of the beta3 subunit. The mice are very hyperactive and hyperresponsive to human contact and other sensory stimuli, and often run continuously in tight circles. When held by the tail, they hold all paws in like a ball, which is frequently a sign of neurological impairment. They have difficulty swimming, walking on grids, and fall off platforms and rotarods, although they do not have a jerky gait. beta3-deficient mice display frequent myoclonus and occasional epileptic seizures, documented by electroencephalographic recording. Hyperactivity, lack of coordination, and seizures are consistent with reduced presynaptic inhibition in spinal cord and impaired inhibition in higher cortical centers and/or pleiotropic developmental defects.

Angelman Syndrome↗
PubMed1996

The clinical spectrum of albinism in humans.

Oculocutaneous albinism is characterized by a congenital reduction or absence of melanin pigment in the skin, hair and eyes. The reduction in the hair and skin results in a change in color but no change in the development or function of these tissues, while the absence of melanin pigment in the eye leads to abnormal development and function. Of particular interest are mutations that are associated with a slow accumulation of pigment in the hair and eyes over time, while retaining the ocular defects of albinism. Analysis of these mutations might provide the insight that we need to understand the interaction between the pigment system and the development of the optic system.

Albinism, Oculocutaneous↗
PubMed1995

One-dimensional genome scanning: identification of the basis of a mouse mutation and identification of genomic changes in ovarian carcinoma.

We have developed a simple one-dimensional electrophoretic method, genome scanning, that can be used to identify large-scale genomic differences between two or more DNA samples. Genome scanning is especially useful in the detection of genetic amplifications, deletions, and rearrangements. The assay is essentially a high-resolution Southern analysis, comparing equivalent amounts of genomic DNA samples that are variant for a given trait. The Southern blots are hybridized to a probe sequence derived from a medium copy number repetitive element (1000-2000 copies per haploid genome) naturally dispersed throughout the genome. The hybridization pattern that results is complex and consists of hundreds of bands. If the DNA samples are otherwise equivalent, a net difference in hybridization intensity between homologous bands of different samples indicates a genetic change. In this report, we discuss the origin of the method, its premise, and review its application to mouse mutational analysis and to human cancer research (a more detailed discussion of the theory is presented elsewhere in this issue; Y. Gondo and M. H. Brilliant, Electrophoresis 1995, 16, 174-178).

Animals↗
PubMed1995

Theoretical basis of one-dimensional genome scanning: a direct method to identify the site of a mutation.

Genome scanning is a technique designed to uncover a net genetic difference between otherwise identical DNA samples. As such, it can be used to directly identify the site of a gene mutation, facilitating the cloning of DNA fragments from that site. Unlike other conventional positional cloning methods, one-dimensional genome scanning does not require prior knowledge of the location of the gene or mutation nor does it require closely linked markers. Rather, this method can directly identify the site of a net genomic change, such as a deletion or duplication caused by a mutation. Thus, the genome scanning method can be used in place of classic positional cloning strategies because prior positioning or mapping of the objective gene is unnecessary. By using this approach, we have identified and cloned a DNA fragment duplicated in the p(un) mutation of the mouse pink-eyed dilution locus (Brilliant et al., Science 1991, 252, 566-569). However, no other similar attempt using one-dimensional genome scanning has been reported so far, in spite of the simplicity of the procedure and its success in identifying and ultimately characterizing the pink-eyed dilution gene of the mouse. The lack of other reports of its success are perhaps not because of the practical difficulties of this method, but may be due to the false presumption that the probability for directly identifying the mutation site using genome scanning is extremely low. The theoretical probability was calculated and is presented here.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Melanosomal tyrosine transport in normal and pink-eyed dilution murine melanocytes.

Tyrosine is the endogenous substrate for melanin production within melanosomes, but the method of tyrosine transport into the melanosome has not been investigated. In the mouse, melanogenesis is disrupted by mutations in the p gene resulting in the pink-eyed dilution phenotype; it has been suggested that the p gene codes for a tyrosine transport protein. We determined that normal (melan-a) melanosome-rich granular fractions take up 10 microns [3H]tyrosine at 21.1 +/- 6.1 (SEM, standard error of the mean) pmol/min/mg protein (N = 7) compared with 21.3 +/- 5.8 SEM pmol/min/mg protein (N = 5) for pink-eyed dilution, whose plasma membrane tyrosine transport was also normal (Km 89 microM; Vmax 302 pmol/min/mg cell protein). We also demonstrated that pink-eyed dilution melanosomes are immature by virtue of their low density, high hexosaminidase activity, and lack of pigment. These data indicate that a tyrosine transport system exists in the melanosomal membrane and that the p gene does not encode a tyrosine transporter of critical importance.

Animals↗
PubMed1994

Identification of a melanosomal membrane protein encoded by the pink-eyed dilution (type II oculocutaneous albinism) gene.

The pink-eyed dilution (p) locus in the mouse is critical to melanogenesis; mutations in the homologous locus in humans, P, are a cause of type II oculocutaneous albinism. Although a cDNA encoded by the p gene has recently been identified, nothing is known about the protein product of this gene. To characterize the protein encoded by the p gene, we performed immunoblot analysis of extracts of melanocytes cultured from wild-type mice with an antiserum from rabbits immunized with a peptide corresponding to amino acids 285-298 of the predicted protein product of the murine p gene. This antiserum recognized a 110-kDa protein. The protein was absent from extracts of melanocytes cultured from mice with two mutations (pcp and p) in which transcripts of the p gene are absent or greatly reduced. Introduction of the cDNA for the p gene into pcp melanocytes by electroporation resulted in expression of the 3.3-kb mRNA and the 110-kDa protein. Upon subcellular fractionation of cultured melanocytes, the 110-kDa protein was found to be present in melanosomes but absent from the vesicular fraction; phase separation performed with the nonionic detergent Triton X-114 confirmed the predicted hydrophobic nature of the protein. These results demonstrate that the p gene encodes a 110-kDa integral melanosomal membrane protein and establish a framework by which mutations at this locus, which diminish pigmentation, can be analyzed at the cellular and biochemical levels.

Albinism, Oculocutaneous↗
PubMed1994

Genome scanning detects genetic alterations in human ovarian carcinoma.

Genome scanning, originally used to detect mouse mutations, is a technique which can rapidly identify differences between genomic DNA samples. The procedure is essentially a high resolution Southern analysis using a probe that hybridizes to a medium copy number (1000-2000 copies per haploid genome) repetitive element naturally dispersed throughout the genome. This technique detects genetic changes (primarily large scale genetic changes, e.g., amplifications and deletions) as differences in hybridization band intensity. The use of a probe derived from an endogenous human retroviral-like repetitive sequence, the RTVL-H element, has made genome scanning in humans feasible. In this report, the genome scanning technique was used to evaluate genomic DNA extracted from 14 frozen ovarian tumors. These included 8 high grade serous cystadenocarcinomas, 2 endometrioid carcinomas, one malignant mixed mullerian tumor, 2 Krukenberg tumors, and one tumor where histological classification was unavailable. Band amplifications were identified in 11 cases, with the most prominent amplifications observed in the high grade serous cystadenocarcinomas. In some of the cases, the amplifications involved bands of identical molecular size suggesting that similar underlying changes occurred in different tumors and are potentially associated with specific histological tumor types or clinical behavior. Band deletions were also observed in one endometrioid tumor where blood leukocyte genomic DNA was available from the same patient, allowing a direct comparison.

DNA Probes↗
PubMed1994

African origin of an intragenic deletion of the human P gene in tyrosinase positive oculocutaneous albinism.

Oculocutaneous albinism (OCA) is a genetically heterogeneous hypopigmentation disorder. One of the two major autosomal recessive forms involves the tyrosinase gene (OCA1), while the other form (OCA2) has recently been associated with alterations of the P gene on chromosome 15. OCA2 is about twice as common as OCA1 in African and African-American populations. We now describe an interstitial deletion that removes a single exon of the P gene. In a large family from an inbred population of tri-racial origin, all individuals with OCA2 were found to be homozygous for this allele. Moreover, the same mutant P allele was detected in several unrelated African American individuals with OCA2, but not in Caucasians with OCA2. The detection of the same allele in two unrelated Africans with OCA2 indicates an African origin for this allele.

Africa↗
PubMed1994

The original pink-eyed dilution mutation (p) arose in Asiatic mice: implications for the H4 minor histocompatibility antigen, Myod1 regulation and the origin of inbred strains.

Allelic variation of the mouse pink-eyed dilution (p) gene in common laboratory strains and wild mice was examined by Southern blot and by polymerase chain reaction. In these assays the original p mutation allele found in strains SJL/J, 129/J, B10.129(21m), P/J and FS/Ei most closely matches an Asian Mus musculus allele, confirming anecdotal accounts of the Asian origin of this mutation. In contrast, the wild-type allele found in other common laboratory strains was apparently derived from Mus domesticus. Analysis of chromosome 7 loci both proximal and distal to the p locus demonstrates that strains SJL/J, 129/J, B10.129(21M), P/J and FS/Ei contain DNA segments of varying length derived from M. musculus. Strains 129/J and B10.129(21M) contain the largest segment of M. musculus-derived DNA (about 5 cM), including the loci Myod1, p, three clustered GABAA receptor subunit loci (Gabrg3, Gabra5 and Gabrb3), and Snrpn. The difference in the species origin of genes from this region of chromosome 7 may underlie the basis of the antigenicity of the minor histocompatibility antigen H4, defined by the strain B10.129(21M), and may account for the enhanced Myod1 activity observed in SJL/J mice.

Alleles↗
PubMed1994

The mouse pink-eyed dilution gene: association with hypopigmentation in Prader-Willi and Angelman syndromes and with human OCA2.

Mutations at the mouse pink-eyed dilution locus, p, cause hypopigmentation. We have cloned the mouse p gene cDNA and the cDNA of its human counterpart, P. The region of mouse chromosome 7 containing the p locus is syntenic with human chromosome 15q11-q13, a region associated with Prader-Willi syndrome (PWS) and Angelman syndrome (AS), both of which involve profound imprinting effects. PWS patients lack sequences of paternal origin from 15q, whereas AS patients lack a maternal copy of an essential region from 15q. However, the critical regions for these syndromes are much smaller than the chromosomal region commonly deleted that often includes the P gene. Hypopigmentation in PWS and AS patients is correlated with deletions of one copy of the human P gene that is highly homologous with its mouse counterpart. A subset of PWS and AS patients also have OCA2. These patients lack one copy of the P gene in the context of a PWS or AS deletion, with a mutation in the remaining chromosomal homologue of the P gene. Mutations in both homologues of the P gene of OCA2 patients who do not have PWS or AS have also been detected.

Albinism, Oculocutaneous↗
PubMed1993

The mouse intracisternal A particle-promoted placental gene retrotransposition is mouse-strain-specific.

Insertion of a single long terminal repeat (LTR) of an intracisternal A particle (IAP) gene into a placenta-expressed cellular gene (mouse IAP-promoted placental gene, MIPP) has recently been found for the mouse strains Swiss and CF-1. To test whether such a retrotransposition event has also taken place in other strains of mouse, genomic DNA and total RNAs were analyzed from the outbred CF-1 strain and five inbred strains of mouse, AKR/J, C57BL/6J, DBA/2J, C3H/HeJ, and BALB/c. Specific DNA fragments flanking the LTR region were isolated from MIPP cDNA and genomic clones and used as hybridization probes. Three transcripts [two minor, 4.4 kilobases (kb) and 2.2 kb; one major, 1.2 kb] were detected. The 4.4-kb and 2.2-kb species were found in all strains of mouse studied. The 1.2-kb transcript (promoted by IAP LTR) is present only in placentas of C3H/HeJ and BALB/c mice. Both of these strains contain an IAP LTR in the MIPP gene. In contrast, there is no IAP LTR in this cellular gene in strains DBA/2J, C57BL/6J, and AKR/J. Thus, the IAP MIPP retrotransposition is strain-specific. The parents of the outbred CF-1 mice used for the present studies were both heterozygous at the MIPP locus. Restriction fragment length polymorphism studies using inbred strains and recombinant inbred mice have further established the linkage between the MIPP gene (D4Jhu8) and several loci on distal mouse chromosome 4. The symbol Ipp is being used for this gene in all major mouse data bases and in the comparative section of the human genome data base.

Alleles↗
PubMed1993

High-frequency genetic reversion mediated by a DNA duplication: the mouse pink-eyed unstable mutation.

The mouse pink-eyed unstable (p(un)) mutation, affecting coat color, exhibits one of the highest reported reversion frequencies of any mammalian mutation and is associated with a duplication of genomic DNA at the p locus. In this study, genomic clones containing the boundaries of the p(un) duplication were isolated and characterized. The structure of these sequences and their wild-type and revertant counterparts were analyzed by restriction mapping, PCR product analysis, DNA sequence analysis, and pulsed-field gel electrophoresis. DNA from p(un) was distinguished from wild-type and revertant DNA by a head-to-tail tandem duplication of approximately 70 kilobases. No differences were detected between revertant and wild-type DNAs. Thus, the reversion in phenotype of p(un) mice is coupled with the loss of one copy of an approximately 70-kilobase duplicated segment. Testable models are presented to account for p(un) reversion.

Alleles↗
PubMed1992

The mouse pink-eyed dilution gene: association with human Prader-Willi and Angelman syndromes.

Complementary DNA clones from the pink-eyed dilution (p) locus of mouse chromosome 7 were isolated from murine melanoma and melanocyte libraries. The transcript from this gene is missing or altered in six independent mutant alleles of the p locus, suggesting that disruption of this gene results in the hypopigmentation phenotype that defines mutant p alleles. Characterization of the human homolog revealed that it is localized to human chromosome 15 at q11.2-q12, a region associated with Prader-Willi and Angelman syndromes, suggesting that altered expression of this gene may be responsible for the hypopigmentation phenotype exhibited by certain individuals with these disorders.

Amino Acid Sequence↗
PubMed1992

Genetic and molecular analysis of recessive alleles at the pink-eyed dilution (p) locus of the mouse.

Recessive mutant alleles at the pink-eyed dilution (p) locus on mouse chromosome 7 reduce pigmentation of both the coat and eyes. Here we describe the properties and complementation interactions of 10 p alleles, including 6 not previously reported. Several alleles that cause additional phenotypes affecting development, reproduction, and behavior were shown to be deletions by using DNA probes derived from the p region. An alignment of functional and marker-defined units is proposed, giving a linear complementation map that orders at least four functional loci. The characterization of a nested set of deletions around p will facilitate detailed molecular analyses of the genes and developmental functions associated with this part of the mouse genome.

Alleles↗