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PubMed2000

Embryonic development is disrupted by modest increases in vascular endothelial growth factor gene expression.

Previous work has shown that heterozygocity for a null mutation of the VEGF-A gene, resulting in a 50% reduction in VEGF-A expression, is embryonic lethal at embroyonic day (E) 9.5 in mice. We now show that two- to threefold overexpression of VEGF-A from its endogenous locus results in severe abnormalities in heart development and embryonic lethality at E12.5-E14. The mutant embryos displayed an attenuated compact layer of myocardium, overproduction of trabeculae, defective ventricular septation and abnormalities in remodeling of the outflow track of the heart. In addition, aberrant coronary development was characterized by formation of oversized epicardial vessels, apparently through vasculogenesis. We infer that embryonic survival requires a narrow window of VEGF-A expression.

3' Untranslated Regions↗
PubMed2005

Embryonic development of choline acetyltransferase and nitric oxide synthase in the spinal cord of pigeons and chickens with special reference to the superficial dorsal horn.

The superficial dorsal horn of birds as well as mammals contains both cholinergic and nitrergic neuronal structures as evident from the presence of the synthesizing enzymes such as choline acetyltransferase and nitric oxide synthase, which is an NADPH diaphorase. In the rat, both systems develop only postnatally. Rats are altricial at birth whereas pigeons and chickens are semiprecocial or precocial, respectively, at the time of hatching. Immunocytochemical studies of choline acetyltransferase and nitric oxide synthase in the developing avian spinal cord (starting with embryonic day 12 of 18 in the pigeon and 14 of 21 in the chicken) showed that both systems are well developed in the superficial dorsal horn at the time of hatching in both avian species. In the pigeon, choline acetyltransferase-positive superficial dorsal horn neurons appear only on the day of hatching (E18), whereas nitric oxide synthase-positive neurons can be first detected at stage E14. In the chicken, nitric oxide synthase-positive neurons are present already at stage E14, whereas choline acetyltransferase-positive neurons appear at stage E20. Autonomic and somatic motor neurons show adult-like choline acetyltransferase-immunoreactivity and/or nitric oxide synthase-immunoreactivity at the earliest stages investigated. It is concluded that the stage of maturation at birth or hatching plays an important role in the development of superficial dorsal horn cholinergic and nitrergic systems.

Animals↗
PubMed1990

In situ hybridization studies on murine catalase mRNA expression during embryonic development.

In situ hybridization using nucleic acid probes was used to detect cell- and tissue-specific transcript(s) of embryonic genes during development and differentiation. This highly sensitive technique has the potential to provide valuable information on the regulation of low-abundance housekeeping genes during development. We have determined the experimental conditions required to detect the catalase message in adult mouse liver. Catalase effects the breakdown of H2O2 to O2 and H2O and offers protection against the toxic effects of oxygen radicals. We used a cloned 550 bp BamHl-Pstl fragment from a mouse catalase cDNA (pMCT-1) to generate 35S-labeled sense and antisense riboprobes. The experimental conditions used were sensitive enough to quantitate the abundance of silver grains generated by the antisense riboprobe on the adult liver, a tissue known to be positive for this message. The hybridization protocol was applied to serial sections of 13- and 18-day-old mouse embryos. The results suggest that the catalase expression in the liver and brain begins with somite formation and increases with development and differentiation. On the other hand, this message appears to be absent in mesenchyme, particularly in day 13 embryos. The message in positive tissues appears evenly distributed throughout the cell. The observed expression of the catalase message in the adult liver is approximately six times that in the embryonic liver. It is compatible with the enzyme activity results and emphasizes the sensitivity of the in situ hybridization method (over northern blot, etc.) used in this study.

Animals↗
PubMed2001

Steroid hormones during embryonic development in Japanese quail: plasma, gonadal, and adrenal levels.

The purpose of this experiment was to measure plasma, gonad, and adrenal steroid hormones during embryonic and early posthatch development in Japanese quail. Blood plasma samples were collected from male and female Japanese quail embryos at 2-d intervals between Day 10 of incubation and Day 5 posthatch. Gonads and adrenal glands were collected from a separate set of embryos at the same ages. Concentrations of androgen (testosterone and 5alpha-dihydrotestosterone) and 17beta-estradiol (E2) were determined by RIA. Plasma androgen changed significantly (P < 0.001) with age in males and females, and there were significant differences (P < 0.001) between sexes in the hormonal patterns. Males had higher plasma androgen than females; conversely, females consistently had overall higher levels of estradiol than males. Adrenal gland steroid content remained relatively high and did not change significantly with age. In contrast, steroid content of gonads followed patterns similar to those observed for plasma levels. These results provide evidence for steroid hormone production by the gonads of both sexes, as well as for distinct differences in the patterns observed in the adrenal gland and gonads. These results provide evidence for gonadal regulation of changes in circulating hormone levels. Further, these hormonal patterns were associated with the timing of steroid-induced sexual differentiation in the Japanese quail, suggesting that plasma gonadal steroids are critical in sexual differentiation.

Adrenal Glands↗
PubMed2005

The dual-specificity protein phosphatase DUSP9/MKP-4 is essential for placental function but is not required for normal embryonic development.

To elucidate the physiological role(s) of DUSP9 (dual-specificity phosphatase 9), also known as MKP-4 (mitogen-activated protein kinase [MAPK] phosphatase 4), the gene was deleted in mice. Crossing male chimeras with wild-type females resulted in heterozygous (DUSP9(+/-)) females. However, when these animals were crossed with wild-type (DUSP9(+/y)) males none of the progeny carried the targeted DUSP9 allele, indicating that both female heterozygous and male null (DUSP9(-/y)) animals die in utero. The DUSP9 gene is on the X chromosome, and this pattern of embryonic lethality is consistent with the selective inactivation of the paternal X chromosome in the extraembryonic tissues of the mouse, suggesting that DUSP9/MKP4 performs an essential function during placental development. Examination of embryos between 8 and 10.5 days postcoitum confirmed that lethality was due to a failure of labyrinth development, and this correlates exactly with the normal expression pattern of DUSP9/MKP-4 in the trophoblast giant cells and labyrinth of the placenta. Finally, when the placental defect was rescued, male null (DUSP9(-/y)) embryos developed to term, appeared normal, and were fertile. Our results indicate that DUSP9/MKP-4 is essential for placental organogenesis but is otherwise dispensable for mammalian embryonic development and highlights the critical role of dual-specificity MAPK phosphatases in the regulation of developmental outcomes in vertebrates.

Alleles↗
PubMed1999

Xenopus muscle-specific kinase: molecular cloning and prominent expression in neural tissues during early embryonic development.

A muscle-specific receptor tyrosine kinase, designated MuSK, mediates agrin-induced aggregation of acetylcholine receptors at the vertebrate neuromuscular junction. cDNAs encoding Xenopus MuSK were isolated from embryonic cDNA libraries. The full-length MuSK cDNA encodes for a polypeptide of 948 amino acids and possesses the features unique to mammalian MuSK, including four Ig-like domains, C6 box, transmembrane region and an intracellular tyrosine kinase domain. Interestingly, Xenopus MuSK also contains a kringle domain similar to that previously reported for Torpedo MuSK. The overall amino acid sequence identity of Xenopus MuSK with mammalian MuSK is approximately 65%. Northern blot analysis demonstrated the presence of three MuSK transcripts (approximately 1 kb, approximately 3 kb and approximately 7 kb) which were differentially expressed during development. The expression of the approximately 7 kb MuSK transcript remained as the predominant species in adult tissues, e.g. skeletal muscle, spleen and lung. Immunocytochemical analysis with a MuSK-specific antibody revealed that Xenopus MuSK was colocalized with AChRs at neuromuscular junctions as well as in spontaneous acetylcholine receptor hot spots of cultured muscle cells. In situ hybridization revealed prominent expression of MuSK transcripts in neural tissues and myotomal muscle during the period of neurulation and synaptogenesis. The MuSK transcript detected at abundant levels in the central nervous system (CNS) was localized to the brain, spinal cord and eye vesicles during early embryonic development. In addition, the MuSK protein in the developing eye was found to be prominently expressed during embryonic stages of 32 and 35. These findings raise an intriguing possibility that, in addition to the known function in the formation of the neuromuscular junctions, MuSK may be involved in neural development.

Agrin↗