Targeted mutagenesis of the endogenous mouse Mis gene promoter: in vivo definition of genetic pathways of vertebrate sexual development.

Mutations were introduced into conserved steroidogenic factor 1 (SF1)- and SOX9-binding sites within the endogenous mouse Mullerian inhibiting substance (Mis) promoter. Male mice homozygous for the mutant SF1-binding site correctly initiated Mis transcription in fetal testes, although at significantly reduced levels. Surprisingly, sufficient MIS was produced to eliminate the MUllerian ducts.

Lim1 is required in both primitive streak-derived tissues and visceral endoderm for head formation in the mouse.

Lim1 is a homeobox gene expressed in the extraembryonic anterior visceral endoderm and in primitive streak-derived tissues of early mouse embryos. Mice homozygous for a targeted mutation of Lim1 lack head structures anterior to rhombomere 3 in the hindbrain. To determine in which tissues Lim1 is required for head formation and its mode of action, we have generated chimeric mouse embryos and performed tissue layer recombination explant assays.

HNF3beta and Lim1 interact in the visceral endoderm to regulate primitive streak formation and anterior-posterior polarity in the mouse embryo.

Recent embryological and genetic experiments have suggested that the anterior visceral endoderm and the anterior primitive streak of the early mouse gastrula function as head- and trunk-organising centers, respectively. Here, we report that HNF3beta and Lim1 are coexpressed in both organising centers suggesting synergistic roles of these genes in regulating organiser functions and hence axis development in the mouse embryo. To investigate this possibility, we generated compound HNF3beta and Lim1 mutant embryos.

Multiple roles for activin-like kinase-2 signaling during mouse embryogenesis.

The members of the transforming growth factor-beta (TGF-beta) superfamily are secreted proteins that interact with cell-surface receptors to elicit signals that regulate a variety of biological processes during vertebrate embryogenesis. Alk2, also known as ActRIA, Tsk7L, and SKR1, encodes a type I TGF-beta family receptor for activins and BMP-7. Initially, Alk2 transcripts are detected in the visceral endoderm of gastrula stage mouse embryos, suggesting a signaling role in extraembryonic tissues during development.

Goosecoid acts cell autonomously in mesenchyme-derived tissues during craniofacial development.

Mice homozygous for a targeted deletion of the homeobox gene Goosecoid (Gsc) have multiple craniofacial defects. To understand the mechanisms responsible for these defects, the behavior of Gsc-null cells was examined in morula aggregation chimeras. In these chimeras, Gsc-null cells were marked with beta-galactosidase (beta-gal) activity using the ROSA26 lacZ allele.

Requirement for Wnt3 in vertebrate axis formation.

Several studies have implicated Wnt signalling in primary axis formation during vertebrate embryogenesis, yet no Wnt protein has been shown to be essential for this process. In the mouse, primitive streak formation is the first overt morphological sign of the anterior-posterior axis. Here we show that Wnt3 is expressed before gastrulation in the proximal epiblast of the egg cylinder, then is restricted to the posterior proximal epiblast and its associated visceral endoderm and subsequently to the primitive streak and mesoderm.

Sequence and genomic organization of the mouse Lim1 gene.

The sequence and genomic organization of the mouse Lim1 gene were determined. The mouse Lim1 gene has five coding exons. The Lim1 transcription initiation start site was determined by 5' RACE.

Isolation of novel cDNAs by subtractions between the anterior mesendoderm of single mouse gastrula stage embryos.

The anterior mesendoderm of mid- to late primitive streak stage mouse embryos has the ability to induce anterior neuroectodermal fate in naive epiblast [S.-L. Ang and J.

Sox9 is required for cartilage formation.

Chondrogenesis results in the formation of cartilages, initial skeletal elements that can serve as templates for endochondral bone formation. Cartilage formation begins with the condensation of mesenchyme cells followed by their differentiation into chondrocytes. Although much is known about the terminal differentiation products that are expressed by chondrocytes, little is known about the factors that specify the chondrocyte lineage.

High specificity of Müllerian-inhibiting substance signaling in vivo.

Female transgenic mice that ectopically express high levels of human Müllerian-inhibiting substance (hMIS) under the control of the mouse metallothionein (MT) promoter lack a uterus, oviducts, and ovaries. The loss of the uterus and oviducts is consistent with the known activities for MIS. However, it is not clear if the loss of the ovaries in these transgenic females is caused by interactions of MIS with its normal receptor signaling pathway or by abnormal interactions with other transforming growth factor-beta (TGF-beta) super family receptor signaling pathways.

Functional analysis of Gscl in the pathogenesis of the DiGeorge and velocardiofacial syndromes.

Gscl encodes a Goosecoid-related homeodomain protein that is expressed during mouse embryogenesis. In situ hybridization and immunohistochemistry studies show that Gscl is expressed in the pons region of the developing central nervous system and primordial germ cells. Gscl expression is also detected in a subset of adult tissues, including brain, eye, thymus, thyroid region, stomach, bladder and testis.

Esx1 is an X-chromosome-imprinted regulator of placental development and fetal growth.

In marsupials and mice, the paternally derived X chromosome is preferentially inactivated in the placental tissues of female embryos. We show here that the X-linked homeobox gene Esx1 (refs 5,6), whose expression is restricted to extraembryonic tissues, is a chromosomally imprinted regulator of placental morphogenesis and trophoblast differentiation. Heterozygous female mice that inherited a mutant Esx1 allele from their father developed normally.

Restricted beta-galactosidase expression of a hygromycin-lacZ gene targeted to the beta-actin locus and embryonic lethality of beta-actin mutant mice.

beta-actin is a cytoskeletal protein that is ubiquitously expressed. To exploit the regulation the beta-actin gene, a promoterless hygromycin-lacZ fusion gene with a splice acceptor was introduced into the first intron of the beta-actin locus by homologous recombination in mouse embryonic stem (ES) cells. The targeted ES cells were hygromycin resistant and expressed beta-galactosidase (beta-gal) activity.

Expression of the mouse cerberus-related gene, Cerr1, suggests a role in anterior neural induction and somitogenesis.

The Xenopus cerberus gene encodes a secreted factor that is expressed in the anterior endomesoderm of gastrula stage embryos and can induce the formation of ectopic heads when its mRNA is injected into Xenopus embryos [Bouwmeester, T., Kim, S., Lu, B.

Transcriptional interferences at the Hoxa4/Hoxa5 locus: importance of correct Hoxa5 expression for the proper specification of the axial skeleton.

We have previously described a Hoxa5 mutant mouse line in which specification of axial identity is perturbed and viability is markedly reduced. In the present study, we assay the Hoxa5 mutation in different genetic backgrounds and carry out a complete analysis of skeletal transformations. Although Hoxa5 is expressed over a large domain during embryogenesis, homeotic transformations of the axial skeleton are confined between cervical vertebra C3 and thoracic vertebra T2, which corresponds to the specific expression domain of the major Hoxa5 transcript.

Overlapping roles and asymmetrical cross-regulation of the USF proteins in mice.

USF1 and USF2 are ubiquitously expressed transcription factors implicated as antagonists of the c-Myc protooncoprotein in the control of cellular proliferation. To determine the biological role of the USF proteins, mutant mice were generated by homologous recombination in embryonic stem cells. USF1-null mice were viable and fertile, with only slight behavioral abnormalities.

Sequential roles for Otx2 in visceral endoderm and neuroectoderm for forebrain and midbrain induction and specification.

The homeobox gene Otx2 is a mouse cognate of the Drosophila orthodenticle gene, which is required for development of the brain, rostral to rhombomere three. We have investigated the mechanisms involved in this neural function and specifically the requirement for Otx2 in the visceral endoderm and the neuroectoderm using chimeric analysis in mice and explant recombination assay. Analyses of chimeric embryos composed of more than 90% of Otx2-/- ES cells identified an essential function for Otx2 in the visceral endoderm for induction of the forebrain and midbrain.

Mouse gastrulation: the formation of a mammalian body plan.

The process of gastrulation is a pivotal step in the formation of the vertebrate body plan. The primary function of gastrulation is the correct placement of precursor tissues for subsequent morphogenesis. There is now mounting evidence that the body plan is established through inductive interactions between germ layer tissues and by the global patterning activity emanating from embryonic organizers.

Sequence, genomic organization, and chromosomal location of the mouse Müllerian-inhibiting substance type II receptor gene.

We have determined the sequence and structure of the mouse Müllerian-inhibiting substance (MIS) type II receptor gene. Sequence comparisons demonstrate that the mouse, rat, rabbit, and human MIS type II receptors are highly conserved. The mouse MIS type II receptor gene is encoded by 11 exons and spans approximately 9-kb.

Esx1, a novel X chromosome-linked homeobox gene expressed in mouse extraembryonic tissues and male germ cells.

A novel paired-like homeobox gene, designated Esx1, was isolated in a screen for homeobox genes that regulate mouse embryogenesis. Analysis of a mouse interspecific backcross panel demonstrated that Esx1 mapped to the distal arm of the X chromosome. During embryogenesis, Esx1 expression was restricted to extraembryonic tissues, including the endoderm of the visceral yolk sac, the ectoderm of the chorion, and subsequently the labyrinthine trophoblast of the chorioallantoic placenta.

Goosecoid and HNF-3beta genetically interact to regulate neural tube patterning during mouse embryogenesis.

The homeobox gene goosecoid (gsc) and the winged-helix gene Hepatic Nuclear Factor-3beta (HNF-3beta) are co-expressed in all three germ layers in the anterior primitive streak and at the rostral end of mouse embryos during gastrulation. In this paper, we have tested the possibility of functional synergism or redundancy between these two genes during embryogenesis by generating double-mutant mice for gsc and HNF-3beta. Double-mutant embryos of genotype gsc(-/-);HNF-3beta(+/-) show a new phenotype as early as embryonic days 8.

Spontaneous calcification of arteries and cartilage in mice lacking matrix GLA protein.

Calcification of the extracellular matrix (ECM) can be physiological or pathological. Physiological calcification occurs in bone when the soft ECM is converted into a rigid material capable of sustaining mechanical force; pathological calcification can occur in arteries and cartilage and other soft tissues. No molecular determinant regulating ECM calcification has yet been identified.

Optimal profile for a Gaussian standing-wave atom-optical lens.

We have used a Gaussian standing-wave atom-optical lens to focus a thermal atomic beam. We examine the effect of variations in the intensity profile along the direction of the atomic beam on the performance of our atom-optical lens. For a constant focal-length atom-optical lens, we find that the resolution and contrast of the standing-wave lens are independent of the intensity profile.