RESUMO
The limb-girdle muscular dystrophies (LGMDs) are a heterogenous group of diseases characterized by shoulder-girdle and pelvic muscle weakness and wasting. LGMD 2E is an autosomal recessively inherited form of the disease caused by mutations in the ß-sarcoglycan (SGCB) gene located at 4q12. In this report, we describe a patient who demonstrates non-Mendelian inheritance of a homozygous missense mutation in SGCB resulting in disease expression. A combination of single-nucleotide polymorphism (SNP) array technology and microsatellite analysis revealed the occurrence of maternal uniparental disomy (UPD) for chromosome 4 in the patient. As a consequence of segmental isodisomy at 4q12, the patient inherited two identical SGCB alleles carrying a missense mutation predicted to result in abnormal protein function. SNP array technology proved to be an elegant means to determine the most probable mechanism of UPD formation in this case, and enabled us to determine the location of recombination events along chromosome 4. In our patient, UPD likely arose from a trisomy rescue event due to maternal meiotic non-disjunction that we speculate may have been caused by abnormal recombination at the pericentromeric region. Maternal UPD 4 is a rare finding, and to our knowledge this is the first reported case of UPD in association with LGMD.
Assuntos
Cromossomos Humanos Par 4/genética , Distrofia Muscular do Cíngulo dos Membros/genética , Polimorfismo de Nucleotídeo Único , Dissomia Uniparental/genética , Adulto , Feminino , Humanos , Masculino , Músculo Esquelético/metabolismo , Mutação , Análise Serial de Proteínas , Sarcoglicanas/genéticaRESUMO
Hereditary non-polyposis colorectal cancer is characterized by mutations in one of the DNA mismatch repair genes, primarily MLH1, MSH2, or MSH6. We report here the identification of a genomic deletion of approximately 11.4 kb encompassing the first two exons of the MSH2 gene in two generations of an Ohio family. By Southern blot analysis, using a cDNA probe spanning the first seven exons of MSH2, an alteration in each of three different enzyme digests (including a unique 13-kb band on HindIII digests) was observed, which suggested the presence of a large alteration in the 5' region of this gene. Mouse-human cell hybrids from a mutation carrier were then generated which contained a single copy each of human chromosome 2 on which the MSH2 gene resides. Southern blots on DNA from the cell hybrids demonstrated the same, unique 13-kb band from one MSH2 allele, as seen in the diploid DNA. DNA from this same monosomal cell hybrid failed to amplify in polymerase chain reactions (PCRs) using primers to exons 1 and 2, demonstrating the deletion of these sequences in one MSH2 allele, and the breakpoints involving Alu repeats were identified by PCR amplification and sequence analysis.
Assuntos
Pareamento Incorreto de Bases/genética , Cromossomos Humanos Par 2/genética , Neoplasias Colorretais Hereditárias sem Polipose/genética , Reparo do DNA/genética , Animais , Autorradiografia , Southern Blotting , Éxons/genética , Feminino , Deleção de Genes , Humanos , Células Híbridas , Masculino , Camundongos , Ohio , Linhagem , Análise de Sequência de DNAAssuntos
Pareamento Incorreto de Bases/genética , Reparo do DNA/genética , Proteínas de Ligação a DNA/genética , Neoplasias do Endométrio/genética , Mutação/genética , Proteínas de Neoplasias/genética , Proteínas Proto-Oncogênicas/genética , Proteínas Adaptadoras de Transdução de Sinal , Adenocarcinoma/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Sequência de Bases , Proteínas de Transporte , Neoplasias Colorretais Hereditárias sem Polipose/genética , Análise Mutacional de DNA , Éxons/genética , Feminino , Mutação da Fase de Leitura/genética , Mutação em Linhagem Germinativa/genética , Humanos , Repetições de Microssatélites/genética , Pessoa de Meia-Idade , Dados de Sequência Molecular , Proteína 1 Homóloga a MutL , Proteína 2 Homóloga a MutS , Mutagênese/genética , Proteínas NuclearesRESUMO
Merocyanine 540 (MC540) is a membrane probe that inserts preferentially into loosely packed domains in the phospholipid bilayer of intact cells. Previous experiments have demonstrated that MC540 will bind to human bone marrow (BM) hematopoietic progenitor cells (HPC). Fractions of mononuclear BM cells expressing high MC540 fluorescence have been shown to be enriched for myeloid progenitors and cells residing in the S/G2 + M phases of the cell cycle. We rationalized that MC540 uptake could be used to distinguish between quiescent and metabolically active cells and, therefore, to fractionate normal and leukemic BM cells and normal mobilized peripheral blood (MPB) cells into functionally distinct groups of progenitors. BM and MPB cells were separated into fractions ranging in fluorescence from MC540Bright to MC540Dim. Cell cycle analysis of these fractions revealed that the MC540Dim fraction of normal and CML BM CD34+ cells constituted the most quiescent fraction, and the MC540Bright fractions from these cell types contained the most actively cycling cells. However, no differences in the percentage of cells in G/G1 were observed between MC540Bright and MC540Dim fractions of MPB CD34+ cells. To investigate if these cell cycle status differences translated into distinct functional properties, the hematopoietic potential of BM CD34+MC540Bright and CD34+MC540Dim cell fractions was analyzed in vitro in long-term BM cultures and limiting dilution analysis (LDA) assays. CD34+MC540Dim cells produced more total and committed progenitor cells in long-term cultures than did the CD34+MC540Bright fraction. The CD34+MC540Dim fraction also contained a 2-fold higher number of long-term hematopoietic culture-initiating cells (LTHCIC) than the CD34+MC540Bright fraction, as defined by LDA assays. These data demonstrate that MC540 can be a useful probe for the isolation of primitive HPC from some hematopoietic tissues and may assist in monitoring structural changes in the phospholipid bilayer during proliferation and differentiation of HPC.
