Differential expression of the epidermal K1 and K10 keratin genes during mouse embryo development.

Induction of genes coding for the K1 and K10 keratins during mouse development was studied by measuring the accumulation of their respective mRNAs in day 10 to 17 embryos using an RNase protection assay. Although these two keratins are coexpressed in the suprabasal layers of the epidermis, it was found that while K1 mRNA was detectable as soon as day 10, K10 mRNA was not detectable before day 12. The expression of these genes at this stage of development was not expected since they are specifically associated with keratinization, a process that does not begin before day 17 of gestation. Histological examination of the epidermis of day 10 to 17 embryos suggests that both genes are induced in cells committed to epidermal differentiation, after stratification has started but before the onset of keratinization. It was also found that the two mRNAs increased in abundance steadily and significantly until day 16 and that, in spite of the expectation that filaments should contain equivalent amounts of each subunit, K1 mRNA remained more abundant than K10 mRNA at all times including in adult epidermis. These observations indicate that the two genes are regulated independently during development.     

Differential expression of decorin and biglycan genes during mouse tooth development.

Small leucine-rich proteoglycans (SLRPs) have a number of biological functions and some of them are thought to regulate collagen mineralizaton in bone and tooth. We have previously identified and immunolocalized two members of the SLRPs family, decorin and biglycan, in bovine tooth/periodontium. To investigate their potential roles in tooth development, we examined the mRNA expression patterns of decorin, biglycan and type I collagen in newborn (day 19) mice tooth germs by in situ hybridization. At this developmental stage, the first maxillary and mandibular molars include stages before and after secretion of the predentin matrix, respectively. The expression of decorin mRNA coincided with that of type I collagen mRNA and was mostly observed in secretory odontoblasts, while the biglycan mRNA was expressed throughout the tooth germ, including pre-secretory odontoblasts/ameloblasts, dental papilla and stellate reticulum. However, its signal in secretory odontoblasts was not as evident as that of decorin. In mandibular incisors, where a significant amount of predentin matrix and a small amount of enamel matrix were already secreted, a similar differential expression pattern was observed. In secretory ameloblasts the biglycan mRNA expression was apparent, while that of decorin was not. These differential expression patterns suggest the distinct roles of biglycan and decorin in the process of tooth development.     

Differential spatio-temporal expression of alpha-dystrobrevin-1 during mouse development

Dystrobrevins are a family of dystrophin-related and dystrophin-associated proteins. alpha-dystrobrevin-1 knockout mice suffer from skeletal and cardiac myopathies. It has been suggested that the pathology is caused by the loss of signalling functions but the exact role of dystrobrevins is largely unknown. We have analysed the spatial and temporal expression of alpha-dystrobrevin-1 during mouse embryogenesis and found striking developmental regulation and distribution patterns. During development this protein was expressed not only in muscle but also in the CNS, sensory organs, epithelia and skeleton. Particularly interesting was the correlation of alpha-dystrobrevin-1 expression with the induction of various differentiation processes in the developing eye, inner ear, pituitary, blood-brain barrier, stomach epithelium and areas of the brain, dorsal root ganglia and spinal cord. In contrast, this specific expression at the induction phase decreased/disappeared at later stages of development.     

MAPK信号通路基因在小鼠肝再生中的表达谱变化

为了分析丝裂原活化蛋白激酶(Mitogen-Activated Protein Kinases,MAPK)信号通路基因在肝再生中的表达图谱,以及探讨MAPK信号通路在肝再生中的作用,文章利用四氯化碳(Carbon Tetrachloride,CCl4)诱导的小鼠肝损伤再生模型对MAPK信号通路基因的表达进行检测.首先,采用CCl4腹腔注射的方法建立小鼠肝损伤再生模型,通过肝脏切片HE染色和测定血清中谷丙转氨酶活性确认模型的质量,然后,在注射CCl4后的第0、0.5、1.5、4.5、7 d分别采集小鼠肝脏样本,应用Affymetrix公司的小鼠基因表达芯片,检测MAPK信号通路中93个基因的差异表达图谱,并用荧光实时定量PCR法验证芯片检测的结果.结果表明,在芯片检测到的93个MAPK信号通路基因中,有31个在肝再生中有不同程度差异表达,且经荧光实时定量RT-PCR检测的结果与基因芯片的结果相符合.基因表达谱芯片技术可以筛选出肝再生中差异表达的基因,在小鼠肝再生中的第0.5和1.5 d,MAPK信号通路中表达水平上调的基因增多,而在第4.5和7 d,则表达水平下调的基因明显增多.这一结果表明MAPK信号通路对肝再生不同阶段的双重调控作用.     

Differential expression of protein S genes during Myxococcus xanthus development

Protein S, the most abundant protein synthesized during development of the fruiting bacterium Myxococcus xanthus, is coded by two highly homologous genes called protein S gene 1 (ops) and protein S gene 2 (tps). The expression of these genes was studied with fusions of the protein S genes to the lacZ gene of Escherichia coli. The gene fusions were constructed so that expression of beta-galactosidase activity was dependent on protein S gene regulatory sequences. Both the gene 1-lacZ fusion and the gene 2-lacZ fusion were expressed exclusively during fruiting body formation (development) in M. xanthus. However, distinct patterns of induction of fusion protein activity were observed for the two genes. Gene 2 fusion activity was detected early during development on an agar surface and could also be observed during nutritional downshift in dispersed liquid culture. Gene 1 fusion activity was not detected until much later in development and was not observed after downshift in liquid culture. The time of induction of gene 1 fusion activity was correlated with the onset of sporulation, and most of the activity was spore associated. This gene fusion was expressed during glycerol-induced sporulation when gene 2 fusion activity could not be detected. The protein S genes appear to be members of distinct regulatory classes of developmental genes in M. xanthus.     

Differential expression of two somatostatin genes during zebrafish embryonic development

We have identified the cDNAs of two new zebrafish preprosomatostatins, PPSS1 and PPSS3, in addition to the previously cloned PPSS2 (Argenton et al., 1999). PPSS1 is the orthologue of mammalian PPSSs, with a conserved C-terminal SS-14 sequence, PPSS2 is a divergent SS precursor and PPSS3 is a cortistatin-like prohormone. Using whole-mount in situ hybridisation, we have analysed the expression of PPSS1 and PPSS2 in zebrafish embryos up to 5 days post fertilisation. PPSS1 was expressed in the developing pancreas and central nervous system (CNS), whereas PPSS2 expression was exclusively pancreatic. In the CNS, PPSS1 was detected in several areas, in particular in the vagal motor nucleus and in cells that pioneer the tract of the postoptic commissure. PPSS1 was also expressed transiently in the telencephalon and spinal motor neurons. In all areas but the telencephalon PPSS1 was coexpressed with islet-1.     

Differential expression of house-keeping genes of Aspergillus nidulans during sexual development

The rpl3 gene and the rpl37 gene for Aspergillus nidulans ribosomal protein L3 (RPL3) and RPL37, which were identified as located on chromosome I and chromosome III, respectively, were isolated from chromosome-specific cosmid libraries. The nucleotide sequences of both of the rpl3 gene and the rpl37 gene identified the ORFs of 392 amino acids and 92 amino acids, respectively. Both of the two genes were present in a single copy. The expression of both genes together with two other house-keeping genes, the rps16 gene for RPS16 and the gene for gamma-actin, was analyzed during sexual development. All four genes showed nearly identical expression patterns in that each gene expression reached its maximum after 2 h, decreased thereafter, and increased again after 30-40 h of induction of sexual development.     

Differential expression of retinoic acid-inducible (Stra) genes during mouse placentation

Several retinoid binding proteins and nuclear receptors are specifically expressed in murine placenta. However, little is known about molecular events and target genes regulated by retinoids during placentation. Here, we report that several retinoic acid-inducible (Stra) genes, originally isolated by a differential screening procedure, exhibit specific expression patterns in mouse placental tissues. Three Stra genes, including the ephrinB1 receptor tyrosine kinase ligand, are prominently expressed in the regions of exchanges between maternal and embryonic circulations, i.e. the yolk sac and/or the labyrinthine zone of the mature placenta. The Meis2 homeobox gene appears to be specifically expressed in maternally-derived cell populations. Three other Stra genes, including the AP-2-related gene AP-2gamma, are differentially expressed in the trophoblastic cell lineage. Thus, retinoids may regulate various signaling pathways in specific placental cell-types.     

Differential expression of two clusters of mouse histone genes

The mouse histone mRNAs coded for by three different cloned DNA fragments have been characterized. Two of these cloned DNA fragments, MM221 and MM291, located on chromosome 13, code for H3, H2b and H2a histone mRNAs, which are expressed at low levels in cultured mouse cells and fetal mice. The other DNA fragment, MM614, located on chromosome 3, codes for an H3 and an H2a mRNA, which are expressed at high levels in these cells. The mRNAs for each histone protein share common coding region sequences, while the untranslated regions of all the genes have diverged significantly, as judged by S1 nuclease mapping. Amino acid substitutions in some H3, H2a and H2b proteins are detected as internal cleavages in the S1 nuclease maps. All of these genes code for replication variant histone mRNAs, which are regulated in parallel with DNA synthesis.