Genesis最新文献

The Polycomb group genes are involved in maintaining long term transcriptional repression of the homeotic genes in both Drosophila and mammals. The mouse eed locus encodes the highly conserved ortholog of the Drosophila ESC protein. To test the functional conservation between the two genes, eed was introduced into the fly to determine whether it could rescue the esc mutant phenotype. eed exerted a dominant negative effect on the leg transformation phenotype associated with the esc mutation. This result is interpreted in light of in vitro protein-protein binding data and in vivo polytene chromosome staining indicating the lack of significant interaction between Eed and fly E(Z), a molecular partner of ESC. genesis 26:67-76, 2000

Proper development of the anterior segment of the mammalian eye is critical for normal ocular function. Indeed, several congenital syndromes associated with anterior segment anomalies can lead to impaired vision and glaucoma. One such syndrome is nail patella syndrome (NPS), caused by haploinsufficiency for the LIM-homeodomain transcription factor LMX1B. Although mutations in LMX1B cosegregate with NPS, whether these mutations cause the glaucoma associated with NPS is not known. Here, we provide evidence that the LIM-homeodomain transcription factor lmx1b is an essential regulator of murine anterior segment development. Mice that are homozygous for a targeted mutation of lmx1b display iris and ciliary body hypoplasia, and cornea stromal defects. In addition, two cDNAs normally downregulated in presumptive cornea, mf1 and mfh1, exhibit persistent expression, while keratocan, a keratin sulfate proteoglycan expressed by keratocytes, is not detected in mutant corneas. Moreover, ultrastructural examination of homozygous mutants indicates that corneal collagen fibrillogenesis is perturbed. Taken together, our studies suggest a developmental etiology for glaucoma in NPS patients and highlight lmx1b as an essential regulator of anterior segment morphogenesis and patterning. genesis 26:15-25, 2000.

The Drosophila homeobox gene tinman plays a critical role in subdividing the early mesoderm. In particular, tinman is absolutely required for formation of the heart and visceral mesoderm. tinman expression is initiated throughout the mesoderm of the trunk region under the control of the bHLH transcription factor encoded by the twist gene, a determinant of all mesoderm. Later, tinman expression is restricted to the dorsal portion of the mesoderm, a process that is directed by decapentaplegic (dpp) whose product (a TGF-beta-related protein) is secreted by the overlaying ectoderm. Further restriction of tinman expression to the cardiac progenitors, in which it will persist throughout development, involves the secreted segmentation gene product encoded by wingless (wg, a Drosophila Wnt gene). Here, we show that strong early expression depends on the synergistic action of an enhancer element at the 5' end of the gene in conjunction with an element in the first intron. Moreover, two distinct enhancer regions are responsible for tinman expression in the heart: one region confers expression in the heart-tube-associated pericardial cells, the other element drives expression in the contractile, myocardial cells. The latter element contains two CREB consensus binding sites that are essential for cardiac-specific expression. genesis 26:55-66, 2000.

Generation of a floxed Presenilin-1 (PS1) allele involved two recombination events in the embryonic stem (ES) cells. First, a targeting vector containing a loxP site in intron 1 and a floxed CMV-HYG/TK double selection cassette in intron 3 was integrated into the PS1 locus by homologous recombination. The use of a negative selection cassette, PGK-DTA, dramatically increased the recombination efficiency within the targeted locus (75-fold). Second, an expression vector encoding Cre recombinase was introduced to excise the floxed CMV-HYG/TK cassette via site-specific recombination. However, all five ES cell clones testing positive for the proper removal of the CMV-HYG/TK cassette also contained a proportion of ES cells in which recombination had occurred between the distal loxP sites in introns 1 and 3, resulting in excision of the entire floxed region. It is therefore critical to screen for possible recombination events involving all 3 loxP sites, in order to identify ES cells clones bearing high proportions of the desired ES cells. genesis 26:5-8, 2000.