The progressive disappearance of acinar cells in Spink3(-/-) mice was due to autophagic cell death and impaired regeneration. Thus, Spink3 has essential roles in the maintenance of integrity and regeneration of acinar cells.

No abstract

We have developed a new exchangeable gene trap vector, pU-17, carrying the intron-lox71-splicing acceptor (SA)-βgeo-loxP-pA-lox2272-pSP73-lox511. The SA contains three stop codons in-frame with the ATG of βgalactosidase/neomycin-resistance fusion gene (βgeo) that can function in promoter trapping. We found that the trap vector was highly selective for integrations in the introns adjacent to the exon containing the start codon. Furthermore, by using the Cre-mutant lox system, we successfully replaced the βgeo gene with the enhanced green fluorescent protein (EGFP) gene, established mouse lines with the replaced clones, removed the selection marker gene by mating with Flp-deleter mice, and confirmed that the replaced EGFP gene was expressed in the same pattern as the βgeo gene. Thus, using this pU-17 trap vector, we can initially carry out random mutagenesis, and then convert it to a gain-of-function mutation by replacing the βgeo gene with any gene of interest to be expressed under the control of the trapped promoter through Cre-mediated recombination.

Estrogen related receptor beta (ERR-beta) is an orphan nuclear receptor specifically expressed in a subset of extra-embryonic ectoderm of post-implantation embryos. ERR-beta is essential for placental development since the ERR-beta null mutants die at 10.5dpc due to the placenta abnormality. Here, we show that the ERR-beta is specifically expressed in primordial germ cells (PGC), obviously another important cell type for reproduction. Expression of the ERR-beta mRNA in embryonic germ cells started at E11.5 as soon as PGC reached genital ridges, and persisted until E15-E16 in both sexes. Immunostaining with anti-ERR-beta antibody revealed that the ERR-beta protein is exclusively expressed in germ cells in both male and female gonads from E11.5 to E16. 5. To study function of the ERR-beta in PGC, we complemented placental defects of the ERR-beta null mutants with wild-type tetraploid embryos, and analyzed germ cell development in the rescued embryos. It was found that development of gonad and PGC was not apparently affected, but number of germ cells was significantly reduced in male and female gonads, suggesting that the ERR-beta appears to be involved in proliferation of gonadal germ cells. The rescued embryos could develop to term and grow up to adulthood. The rescued ERR-beta null male were found to be fertile, but both male and female null mutants exhibited behavioural abnormalities, implying that the ERR-beta plays important roles in wider biological processes than previously thought.

Human transthyretin (TTR) has about 110 variants, more than 90 of which are associated with human amyloidosis. Several groups have generated transgenic mice that carry various mutant TTR genes. However, formation of mouse/human TTR heterotetramers has been shown to be inhibitory to dissociation and subsequent amyloid formation. To avoid the effect of mouse Ttr and produce humanized mice carrying different TTR variants at high efficiency, we first produced a null allele in the mouse transthyretin locus using targeting vector that contained a neomycin resistance gene flanked by lox71 and loxP. Then, through Cre‐mediated recombination, we created a replacement allele that carried either a human normal (Val30) or mutant (Met30) TTR cDNA. This replacement resulted in a humanized TTR mouse with similar tissue‐specific profile of human TTR as that of the endogenous mouse Ttr gene. The expression levels of human TTR mRNA and protein in the liver of homozygous human TTR (Val30/Val30) mice were about twice those of heterozygous mouse/human TTR (+/Val30) mice. However, the serum human TTR levels in the Val30/Val30 mice were much less than those in the +/Val30 mice. This contradictory expression was due to unstable Val30 tetramers caused by low binding affinity to mouse retinol binding protein.