Drosophila embryos lacking N-myristoyltransferase have multiple developmental defects

Lipid modification of proteins by the addition of myristic acid to the N-terminal is important in a number of critical cellular processes, for example, signal transduction and the modulation of membrane association by myristoyl switches. Myristic acid is added to proteins by the enzyme N-myristoyltransferase (NMT) and in this paper we detail the effects on embryonic development of a null mutation in the Drosophila NMT gene. Mutant embryos display a range of phenotypes, including failures of head involution, dorsal closure, and germ-band retraction, morphogenetic processes that require cellular movements. Embryos with milder phenotypes have more specific defects in the central nervous system, including thinning of the ventral nerve chord and, in some embryos, specific scission at parasegment 10. Staining of mutant embryos with phalloidin shows that the mutant embryos have a disrupted actin cytoskeleton and abnormal cell morphology. These phenotypes are strikingly similar to those caused by genes involved in dynamic rearrangement of the actin cytoskeleton. For example the myristoylated nonreceptor tyrosine kinases Dsrc42A and Dsrc64B were shown recently to be key regulators of dorsal closure. In addition, analysis of cell death reveals widespread ectopic apoptosis. Our findings are consistent with the hypothesis that the myristoyl switches and signaling pathways characterized at the biochemical level have important functions in fundamental morphogenetic processes.     

Effects of temperature, sorbitol, alanine and diapause hormone on the embryonic development in Bombyx mori: in vitro tests of old hypotheses

Abstract.  An in vitro culture method is described in which embryonic development in Bombyx mori is traced at various temperatures and treatments. The results show that the induction, intensification and termination of diapause are distinct processes. Prediapause embryos, explanted from 40-h-old diapause-destined eggs and cultured in Grace's medium, continue to develop to the appendage-formation stage without arrest, which indicates that the isolated embryos have not entered diapause, whereas the development of embryos from diapausing eggs (15 days after being laid) is significantly slower. The rate of development of embryos dissected from diapause eggs increases during chilling (5 °C) and incubation (at 25 °C) gradually during chilling and dramatically at 25 °C. The in vitro experiments also reveal that sorbitol directly inhibits the development of embryos explanted from diapausing eggs but has no affect on the development of embryos from prediapause eggs. Neither alanine nor diapause hormone prevent isolated embryos from developing.     

Drosophila Embryos Lacking N-Myristoyltransferase Have Multiple Developmental Defects

Lipid modification of proteins by the addition of myristic acid to the N-terminal is important in a number of critical cellular processes, for example, signal transduction and the modulation of membrane association by myristoyl switches. Myristic acid is added to proteins by the enzyme N-myristoyltransferase (NMT) and in this paper we detail the effects on embryonic development of a null mutation in the Drosophila NMT gene. Mutant embryos display a range of phenotypes, including failures of head involution, dorsal closure, and germ-band retraction, morphogenetic processes that require cellular movements. Embryos with milder phenotypes have more specific defects in the central nervous system, including thinning of the ventral nerve chord and, in some embryos, specific scission at parasegment 10. Staining of mutant embryos with phalloidin shows that the mutant embryos have a disrupted actin cytoskeleton and abnormal cell morphology. These phenotypes are strikingly similar to those caused by genes involved in dynamic rearrangement of the actin cytoskeleton. For example the myristoylated nonreceptor tyrosine kinases Dsrc42A and Dsrc64B were shown recently to be key regulators of dorsal closure. In addition, analysis of cell death reveals widespread ectopic apoptosis. Our findings are consistent with the hypothesis that the myristoyl switches and signaling pathways characterized at the biochemical level have important functions in fundamental morphogenetic processes.