Coadaptation in mother and infant regulated by a paternally expressed imprinted gene

This study investigates how a targeted mutation of a paternally expressed imprinted gene regulates multiple aspects of foetal and post-natal development including placental size, foetal growth, suckling and post-natal growth, weaning age and puberty onset. This same mutation in a mother impairs maternal reproductive success with reduced maternal care, reduced maternal food intake during pregnancy, and impaired milk let-down, which in turn reduces infant growth and delays weaning and onset of puberty. The significance of these coadaptive traits being synchronized in mother and offspring by the same paternally expressed imprinted gene ensures that offspring that have extracted 'good' maternal nurturing will themselves be both well provisioned and genetically predisposed towards 'good' mothering.     

Identification of the mouse paternally expressed imprinted gene Zdbf2 on chromosome 1 and its imprinted human homolog ZDBF2 on chromosome 2

In mammals, both the maternal and paternal genomes are necessary for normal embryogenesis due to parent-specific epigenetic modification of the genome during gametogenesis, which leads to non-equivalent expression of imprinted genes from the maternal and paternal alleles. In this study, we identified a paternally expressed imprinted gene, Zdbf2, by microarray-based screening using parthenogenetic and normal embryos. Expression analyses showed that Zdbf2 was paternally expressed in various embryonic and adult tissues, except for the placenta and adult testis, which showed biallelic expression of the gene. We also identified a differentially methylated region (DMR) at 10 kb upstream of exon 1 of the Zdbf2 gene and this differential methylation was derived from the germline. Furthermore, we also identified that the human homolog (ZDBF2) of the mouse Zdbf2 gene showed paternal allele-specific expression in human lymphocytes but not in the human placenta. Thus, our findings defined mouse chromosome 1 and human chromosome 2 as the loci for imprinted genes.     

SCOP, a novel gene product expressed in a circadian manner in rat suprachiasmatic nucleus

To elucidate the mechanism of the circadian rhythm, genes differentially expressed during subjective day and night in the rat suprachiasmatic nucleus (SCN), a circadian oscillator in mammals, were surveyed by a differential display method. We isolated a novel gene, scop (SCN circadian oscillatory protein), that was expressed in a circadian manner in the SCN. SCOP protein is predominantly expressed in the brain and has domains including a pleckstrin homology domain, leucine-rich repeats, a protein phosphatase 2C-like domain and a glutamine-rich region. The structural feature of SCOP protein suggests its role in the intracellular signaling in the SCN.     

A novel sheep gene,MMP7, differentially expressed in muscles from black-boned sheep and local common sheep

Differences in gene expression in muscles from Chinese black-boned sheep and local common sheep were investigated using mRNA differential display. One differentially expressed novel gene was identified through semi-quantitative RT-PCR, and the full-length cDNA sequence was then obtained using the rapid amplification of cDNA ends (RACE). The nucleotide sequence of this gene is not homologous to any of the known sheep genes, but it contains an open reading frame encoding a protein of 416 amino acids, which has high homology with matrix metallopeptidase 7 (matrilysin, uterine) (MMP7) of 10 species: bovine (93%), rhesus monkey (75%), human (74%), pig (73%), chimpanzee (73%), dog (73%), horse (72%), mouse (66%), rat (65%), and chicken (53%). Thus the novel gene can be defined as the sheepMMP7 gene. It was finally assigned to GeneID: 100192317. The phylogenetic tree analysis revealed that the sheepMMP7 gene is closely related to the bovineMMP7. Our experiment is the first one to establish the primary foundation for further research on the sheepMMP7 gene.     

AMPK regulates circadian rhythms in a tissue- and isoform-specific manner

Background

AMP protein kinase (AMPK) plays an important role in food intake and energy metabolism, which are synchronized to the light-dark cycle. In vitro, AMPK affects the circadian rhythm by regulating at least two clock components, CKIα and CRY1, via direct phosphorylation. However, it is not known whether the catalytic activity of AMPK actually regulates circadian rhythm in vivo.

Methodology/Principal Finding

The catalytic subunit of AMPK has two isoforms: α1 and α2. We investigate the circadian rhythm of behavior, physiology and gene expression in AMPKα1−/− and AMPKα2−/− mice. We found that both α1−/− and α2−/− mice are able to maintain a circadian rhythm of activity in dark-dark (DD) cycle, but α1−/− mice have a shorter circadian period whereas α2−/− mice showed a tendency toward a slightly longer circadian period. Furthermore, the circadian rhythm of body temperature was dampened in α1−/− mice, but not in α2−/− mice. The circadian pattern of core clock gene expression was severely disrupted in fat in α1−/− mice, but it was severely disrupted in the heart and skeletal muscle of α2−/− mice. Interestingly, other genes that showed circadian pattern of expression were dysreguated in both α1−/− and α2−/− mice. The circadian rhythm of nicotinamide phosphoryl-transferase (NAMPT) activity, which converts nicotinamide (NAM) to NAD⁺, is an important regulator of the circadian clock. We found that the NAMPT rhythm was absent in AMPK-deficient tissues and cells.

Conclusion/Significance

This study demonstrates that the catalytic activity of AMPK regulates circadian rhythm of behavior, energy metabolism and gene expression in isoform- and tissue-specific manners.     

Identification and partial characterization of FRAG-6, a novel interferon-stimulated gene that is expressed in an IRF-1-INDEPENDENT manner.

In order to identify new interferon-stimulated genes that could help in the better understanding of the mechanism of action of interferons (IFNs), we decided to compare, by differential display RT-PCR (DDRT-PCR), the pattern of gene expression between IFN-alpha treated and untreated mouse embryonic fibroblasts (MEFs). Here we describe the initial characterization of a new cDNA fragment, named FRAG-6, that is expressed only upon IFN stimulation. The IFN-induced expression of this new gene can be observed in both wild-type and IRF-1-deficient MEF. FRAG-6 cDNA hybridizes with an mRNA of 6-9 kb that is induced by IFNs in a time-dependent manner. Analysis of the cloned nucleotide sequence revealed a 174 amino acid (aa) open reading frame (ORF) contained within the 576 bp. No significant homology with known nucleotide or protein sequences was observed. FRAG-6 is induced in vitro upon treatment of wild type or IRF-1-null cells with IFN-alpha or -gamma, but not with TNF or IL-1. Treatment of mice with imiquimod, a potent inducer of IFN, led to induced expression of FRAG-6 mRNA in various organs from wild type or IRF-1-deficient mice, but not from STAT-1 or type I IFN receptor deficient animals. Our results demonstrate that FRAG-6 mRNA induction by interferons is IRF-1-independent and it is likely to be activated by the JAK/STAT pathway. Further characterization of FRAG-6 will help us in the understanding of the mechanism of action of IFNs.     

sox30: a novel zebrafish sox gene expressed in a restricted manner at the midbrain-hindbrain boundary during neurogenesis

 The Sox family of proteins is thought to act to regulate gene expression in a wide variety of developmental processes. Here we describe the cloning of sox30, a novel sox gene from the zebrafish (Danio rerio). In situ hybridization shows that sox30 is expressed in a restricted manner at the boundary between the midbrain and hindbrain during nervous system development. This expression pattern is in direct contrast to that of most other neuronally expressed Sox genes which are expressed throughout the nervous system. Received: 30 October 1998 / Accepted: 1 February 1999     

Alternative splicing of transcripts expressed by the Manduca sexta allatotropin (Mas-AT) gene is regulated in a tissue-specific manner

The Manduca allatotropin (Mas-AT) gene is expressed as at least three mRNA isoforms that differ from each other by alternative splicing. The location at which the alternative exons are included in the mature mRNAs occur within the open reading frame, so that three different propeptides are predicted as translation products. In the pharate adult insect, the major mRNA isoform expressed in the brain and frontal ganglion differs from that expressed in the nerve cord. Examination of the deduced translations of the alternative exons reveals the presence of three additional Mas-AT-like sequences that are flanked by basic amino acid residues. Therefore, the Mas-AT-like sequences present within the gene may be derived from a duplication of an ancestral Mas-AT-like sequence followed by divergence.     

Evidence that an imprinted gene on the X chromosome increases ovulation rate in sheep

Ovulation rate records from 1311 female progeny of 50 Coopworth rams were used to study the inheritance of ovulation rate in a screened high prolificacy sheep flock. Breeding values (BV) for ovulation rate for 33 sires used within the screened flock and ovulation rate deviations for a further 17 sires progeny tested in commercial flocks suggest that a major gene (WOODLANDS: gene) for ovulation rate with a non-Mendelian inheritance pattern is segregating in a family line. Rams assigned as carriers of the putative gene did not produce carrier sons (zero of three), and this coupled with the observation that daughters of carrier rams had ovulation rates of 0. 39 (standard error of difference [SED] = 0.06) higher than contemporaries without a significant increase in the variance of log ovulation rate strongly suggests that the gene is on the X chromosome. The evidence suggests that the gene is also maternally imprinted because ovulation rate data indicate that it is expressed where females inherit a paternal allele but is silenced when inherited on a maternal allele. Maternal granddaughters of carrier rams had mean ovulation rates that were only 0.02 (SED = 0.06) higher than noncarrier ewes from the same flock. Furthermore, carrier dams expressing the gene (paternal allele) had 24 sons, none of which had female offspring that expressed the gene, whereas carrier dams not expressing the gene (maternal allele) had 7 out of 17 sons that had female progeny expressing the gene. There is no evidence of the infertility that occurs in homozygous ewes carrying the X-linked Inverdale gene. Collectively, these results suggest the existence of a novel gene for prolificacy located on the X chromosome that is maternally imprinted. The WOODLANDS: gene was only expressed upon paternal inheritance from carrier males that were the progeny of nonexpressing carrier dams. The gene was not expressed in ewes that received it from either carrier dams (expressing or nonexpressing) or from carrier males that were the progeny of expressing carrier dams.     

Developmental control of a promoter-specific factor that is also regulated by the E1A gene product

We have detected a cellular factor in F9 teratocarcinoma cells that recognizes an adenovirus E1A inducible promoter. This factor, termed E2F, was previously identified in HeLa cells and was found at increased levels as a function of the E1A gene product. Upon differentiation of F9 cells with retinoic acid and cAMP, the factor declines to near undetectable levels, consistent with the control of this factor by E1A and the presence of a cellular E1A-like activity in F9 cells but not in differentiated F9 cells. Finally, if the E1A gene is introduced into differentiated cells by an adenovirus infection, there is a large increase in the level of the factor. We suggest that the control of E2F during F9 differentiation is indeed due to an E1A-like activity.     

A knockout mouse approach reveals that TCTP functions as an essential factor for cell proliferation and survival in a tissue- or cell type-specific manner

Translationally controlled Tumor Protein (TCTP) is an evolutionally highly conserved protein which has been implicated in many cellular functions that are related to cell growth, death, and even the allergic response of the host. To address the physiological roles of TCTP, we generated TCTP knockout mice by targeted gene disruption. Heterozygous mutants appeared to be developmentally normal. However, homozygous mutants (TCTP(-/-)) were embryonic lethal. TCTP(-/-) embryos were smaller in size than the control littermates at all postimplantation stages examined. Although TCTP is widely expressed in both extraembryonic and embryonic tissues, the most prominent defect of the TCTP(-/-) embryo at embryonic stage day 5.5 (E5.5) was in its epiblast, which had a reduced number of cells compared with wild-type controls. The knockout embryos also suffered a higher incidence of apoptosis in epiblast starting about E6.5 and subsequently died around E9.5-10.5 with a severely disorganized structure. Last, we demonstrated that TCTP(-/-) and control mouse embryonic fibroblasts manifested similar proliferation activities and apoptotic sensitivities to various death stimuli. Taken together, our results suggest that despite that TCTP is widely expressed in many tissues or cell types, it appears to regulate cell proliferation and survival in a tissue- or cell type-specific manner.