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G Radice

Publications and source records attributed to G Radice.

9 recordsLinked to original sources
PubMed2001

Rescuing the N-cadherin knockout by cardiac-specific expression of N- or E-cadherin.

Cell-cell adhesion mediated by some members of the cadherin family is essential for embryonic survival. The N-cadherin-null embryo dies during mid-gestation, with multiple developmental defects. We show that N-cadherin-null embryos expressing cadherins using muscle-specific promoters, alpha- or beta-myosin heavy chain, are partially rescued. Somewhat surprisingly, either N-cadherin or E-cadherin was effective in rescuing the embryos. The rescued embryos exhibited an increased number of somites, branchial arches and the presence of forelimb buds; however, in contrast, brain development was severely impaired. In rescued animals, the aberrant yolk sac morphology seen in N-cadherin-null embryos was corrected, demonstrating that this phenotype was secondary to the cardiac defect. Dye injection studies and analysis of chimeric animals that have both wild-type and N-cadherin-null cells support the conclusion that obstruction of the cardiac outflow tract represents a major defect that is likely to be the primary cause of pericardial swelling seen in null embryos. Although rescued embryos were more developed than null embryos, they were smaller than wild-type embryos, even though the integrity of the cardiovascular system appeared normal. The smaller size of rescued embryos may be due, at least in part, to increased apoptosis observed in tissues not rescued by transgene expression, indicating that N-cadherin-mediated cell adhesion provides an essential survival signal for embryonic cells. Our data provide in vivo evidence that cadherin adhesion is essential for cell survival and for normal heart development. Our data also show that E-cadherin can functionally substitute for N-cadherin during cardiogenesis, suggesting a critical role for cadherin-mediated cell-cell adhesion, but not cadherin family member-specific signaling, at the looping stage of heart development.

Animals↗
PubMed1999

Adhesive subdivisions intrinsic to the epithelial somites.

Developing somites express two subtypes of classic cadherin adhesion receptors, N-cadherin and cadherin-11 (cad11). To investigate the role of these adhesion molecules in somite morphogenesis, we analyzed the somites of mice whose N-cadherin and cad11 genes were disrupted. The epithelial somites of N-cadherin null mutant mice were fragmented as reported, whereas those of cad11(-/-) mice showed no structural anomaly. In mice double homozygous for N-cadherin and cad11 mutation, however, somites were further fragmented into smaller clusters than in the N-cadherin-deficient mice, suggesting that these two cadherins cooperate in the maintenance of epithelial somites. Despite the disorganization of epithelial structures, dorsoventral polarity markers were expressed in their correct patterns in all of these mutant somites. Uncx4.1, whose expression is localized only in the caudal region of each somite, was also expressed in a normal pattern in the mutant somites. However, the staining for Uncx4.1 revealed that, in the N-cadherin mutants, each somite tended to be cleaved at the border between the Uncx4. 1-positive and -negative regions and that the cleaved subunits maintained the clustered state, often exhibiting epithelioid morphology. This separation of the rostral and caudal regions was observed as soon as the epithelial somites had been formed. In the N-cadherin/cad11 double-homozygous mutants, this tendency was also observed, although each half of the somite further disintegrated into randomly arranged cell clusters. These results suggest that cells of the rostral and caudal regions of each epithelial somite have an activity to aggregate independently or separate from one another and that one role of N-cadherin and cad11 is to connect the two halves into a single unit.

Animals↗
PubMed1992

Identification and characterization of a novel, evolutionarily conserved gene disrupted by the murine H beta 58 embryonic lethal transgene insertion.

The H beta 58 transgenic mouse line carries a recessive insertional mutation that results in developmental abnormalities beginning at day 7.5 p.c. and embryonic arrest at about day 9.5. In this paper, we describe the characterization of a novel gene encoded at the H beta 58 locus, whose disruption appears to be responsible for the mutant phenotype. The wild-type H beta 58 gene encodes a single 2.7 kb mRNA during embryonic and fetal development, and in many adult somatic tissues. In the mutant locus, this transcription unit is split by the transgene insertion, and one of its coding exons is deleted. Consistent with the physical disruption of the gene, the level of the H beta 58 mRNA in heterozygous mutant mouse tissues was half the normal level, indicating that the mutant allele fails to encode a stable mRNA. In situ hybridization studies revealed that expression of the wild-type H beta 58 gene begins in the oocyte, and continues throughout pre- and post-implantation embryogenesis, despite the fact that homozygous mutant embryos develop successfully through the egg cylinder stage (day 6.5 p.c.). In the early post-implantation embryo, expression of the normal H beta 58 gene is relatively low in the embryonic ectoderm, the tissue displaying the earliest phenotypic effects of the mutation, and highest in the visceral endoderm. We therefore propose that the effects of the mutation on the embryonic ectoderm may be exerted indirectly, via the visceral endoderm. Sequence analysis of H beta 58 cDNA clones revealed no homology between the 38 x 10(3) M(r) H beta 58 protein and other known proteins. However, the H beta 58 gene displayed extremely strong conservation between mammals and birds (greater than 96% amino acid identity), although it appeared less conserved in amphibians and invertebrates.

Amino Acid Sequence↗
PubMed1991

H beta 58, an insertional mutation affecting early postimplantation development of the mouse embryo.

The generation and analysis of insertional mutations affecting mouse embryogenesis provides a powerful method to identify new genes that function in early development. In this paper, we describe an insertional mutation that interferes with postimplantation mouse development beginning at the time of gastrulation. Embryos homozygous for the H beta 58 transgenic insertion developed normally through the early postimplantation, egg cylinder stage (day 6.5 of development). At the primitive streak stage (day 7.5), however, they began to display characteristic abnormalities, including a retardation in the growth of the embryonic ectoderm (the earliest identifiable defect), and in some cases abnormalities of the amnion and chorion. Homozygotes continued to develop for 2-3 more days, reaching the size of a normal 8.5 day embryo, and formed tissues representative of all three germ layers, including several differentiated cell types. The site of insertion was mapped, by a combination of cytogenetic and genetic methods, to chromosome 10, and it appeared to define a new genetic locus. The inserted transgene provided a probe to clone and characterize the mutant locus, as well as the corresponding wild-type locus. In addition to an insertion of 10-20 copies of the transgene, the mutant locus contained a deletion of 2-3 kb of DNA found at the wild-type locus, and possibly an insertion of mouse repetitive DNA. However, genomic sequences on both sides of the insertion site remained co-linear in the wild-type and mutant genomes, and no chromosomal abnormalities could be detected. Five single copy DNA probes spanning the insertion site were tested for their ability to hybridize to RNA from 8.5 day embryos; one of the probes (located within the region deleted from the mutant chromosome) hybridized to a 2.7 kb mRNA encoded at the H beta 58 locus, thus identifying a gene whose disruption appears to be responsible for the mutant phenotype.

Animals↗
PubMed1989

Insertional mutations in transgenic mice.

Insertional mutagenesis represents a promising approach to the identification of new genes involved in mammalian development. In this paper, we have presented a brief review of the literature on the analysis of mutations caused by DNA and retroviral insertion into the mouse genome. We have discussed several methods that we and others have used to identify recessive insertional mutations among transgenic mouse lines. Finally, we have summarized the results of our studies to date on three recessive prenatal lethal mutations that we have identified.

Animals↗
PubMed1986

Tissue-specific DNase I hypersensitive sites in a foreign globin gene in transgenic mice.

We have investigated the DNase I hypersensitivity of a hybrid mouse/human beta-globin gene in erythroid and non-erythroid cells of transgenic mice, to examine the relationship between the chromatin structure and the expression of an exogenous gene. The hybrid globin gene was previously shown to be expressed specifically in erythroid cells in some transgenic lines. The maximal level of hybrid globin mRNA accumulation was a few percent of the endogenous level, and we show here that this results from a low rate of transcription. In erythroid cells from two transgenic lines in which the hybrid gene is expressed, we detect a set of DNase I hypersensitive sites whose locations are indistinguishable from those in endogenous beta-globin genes. The hybrid globin gene contains no DNase I hypersensitive sites in transgenic mouse brain cells. Thus, the tissue-specific expression of the exogenous globin gene is reflected in, and perhaps mediated by, tissue-specific changes in chromatin structure.

Animals↗
PubMedDate not supplied

Specific expression of a foreign beta-globin gene in erythroid cells of transgenic mice.

The globin gene family represents an attractive system for the study of gene regulation during mammalian development, as its expression is subject to both tissue-specific and temporal regulation. While many aspects of globin gene structure and expression have been described extensively, relatively little is known about the cis-acting DNA sequences involved in the developmental regulation of globin gene expression. To begin to experimentally define these regulatory sequences, we have taken the approach of introducing cloned globin genes into the mouse germ line and examining their expression in the resulting transgenic animals. Here we describe a series of transgenic mice carrying a hybrid mouse/human adult beta-globin gene, several of which express the gene exclusively or predominantly in erythroid tissues. These studies demonstrate that regulatory sequences closely linked to the beta-globin gene are sufficient to specify a correct pattern of tissue-specific expression in a developing mouse, when the gene is integrated at a subset of foreign chromosomal positions.

Animals↗