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Biomedical subjects

X Xiang

Publications and source records attributed to X Xiang.

54 records · Page 3Linked to original sources
PubMed1995

NudF, a nuclear migration gene in Aspergillus nidulans, is similar to the human LIS-1 gene required for neuronal migration.

During a study of the genetics of nuclear migration in the filamentous fungus Aspergillus nidulans, we cloned a gene, nudF, which is required for nuclear migration during vegetative growth as well as development. The NUDF protein level is controlled by another protein NUDC, and extra copies of the nudF gene can suppress the nudC3 mutation. nudF encodes a protein with 42% sequence identity to the human LIS-1 (Miller-Dieker lissencephaly-1) gene, which is required for proper neuronal migration during brain development. This strong similarity suggests that the LIS-1 gene product may have a function similar to that of NUDF and supports previous findings to suggest that nuclear migration may play a role in neuronal migration.

Amino Acid Sequence↗
PubMed1995

An alpha tubulin mutation suppresses nuclear migration mutations in Aspergillus nidulans.

Microtubules and cytoplasmic dynein, a microtubule-dependent motor, are required for nuclei to move along the hyphae of filamentous fungi. Nuclear migration in Aspergillus nidulans is blocked by heat-sensitive (hs-) mutations in the nudA gene, which encodes dynein heavy chain, and the nudF gene, which encodes a G protein beta-subunit-like protein. Hs- mutations in the nudC and nudG genes also prevent nuclear migration. We have isolated extragenic suppressor mutations that reverse the hs- phenotypes caused by these mutations. Here we show that one nudF suppressor also suppresses hs- mutations in nudA, nudC, and nudG and deletions in nudA and nudF. This suppressor mutation is in the tubA alpha tubulin gene, and its characteristics suggest that it destabilizes microtubules. The mutation alters microtubule staining and confers sensitivity to cold and benomyl, two treatments that destabilize microtubules. Treatment with low concentrations of benomyl also suppresses the hs- nudA, nudC, nudF, and nudG mutations and the nudA and nudF deletions. Suppression of the hs- nudA mutation and the nudA deletion is especially interesting because these strains lack active dynein heavy chain. Together, these results suggest that microtubule destabilization allows nuclei to migrate even in the absence of cytoplasmic dynein motor function.

Aspergillus nidulans↗
PubMed1994

Cytoplasmic dynein is involved in nuclear migration in Aspergillus nidulans.

Nuclear migration plays an important role in the growth and development of many organisms including the multinuclear fungus Aspergillus nidulans. We have identified four genes, nudA, nudC, nudF, and nudG, in which temperature-sensitive mutations affect nuclear distribution. In this report, we describe the cloning of the nudA gene by complementation of the mutant phenotype by using a chromosome VIII-specific cosmid library. A genomic fragment of nudA hybridized to an mRNA of approximately 14 kb. Sequencing analysis of nudA revealed four ATP-binding sites that are characteristic of the cytoplasmic dynein heavy chain. The amino acid sequence of the nudA gene product shows 52% overall identity with the rat brain cytoplasmic dynein heavy chain. Our study provides in vivo evidence that dynein, a microtubule motor molecule, plays a role in the nuclear migration process.

Adenosine Triphosphate↗
PubMed1992

The gene for the helix-loop-helix protein, Id, is specifically expressed in neural precursors.

While mammalian neurogenesis has been characterized extensively, the molecules involved in regulating neural cell determination and differentiation remain ill-defined. There is accruing evidence that various members of the basic helix-loop-helix (bHLH) protein family critically regulate these biological processes in a number of tissues. Id, a negative regulator of bHLH proteins, was found to exhibit peak gene expression during mouse embryogenesis with a striking pattern in the central nervous system. Id transcripts were specifically localized to undifferentiated neural precursors of the ventricular zone and were not present in their differentiated derivatives. In addition, in the peripheral nervous system, dorsal root ganglia sensory precursors, known to be undifferentiated while dividing, also expressed Id mRNA. However, in the sympathetic nervous system and adrenal medulla, where differentiation and division occur simultaneously in precursors, Id was not expressed. Since Id transcript abundance inversely correlated with differentiation, this protein, similar to its Drosophila homolog, extramacrochaetae, may play a negative regulatory role in neural differentiation.

Animals↗
PubMed1990

Mini-mouse: disruption of the pygmy locus in a transgenic insertional mutant.

A founder transgenic mouse harbored two different integration patterns of a transgene at the same locus, each of which gave rise to a similar autosomal recessive mutation. Mice of the mutant phenotype were of small stature but had normal levels of growth hormone. The disrupted locus was cloned, and a genetic and molecular analysis showed that the insertional mutants were allelic to a spontaneous mutant, pygmy. The mice should be a useful model for the growth hormone-resistant human dwarf syndromes and could lead to a greater understanding of the pathways involved in growth and development.

Animals↗