vnd, a gene required for early neurogenesis of Drosophila, encodes a homeodomain protein.

Abstract

The development of the central nervous system in Drosophila is initiated by the segregation of neuroblasts, the neural progenitors, from the embryonic neuroectoderm. This process is guided by at least two classes of genes: the achaete‐scute complex (AS‐C) proneural genes and the neurogenic genes. It has been known for some time that loss‐of‐function mutations in the AS‐C result in neural hypoplasia and the first observed defect is failure of segregation of a fraction of neuroblasts. Loss‐of‐function mutations at the ventral nervous system defective (vnd) locus are known to lead to similar phenotypic defects in early neurogenesis. More recently, the vnd locus has been implicated in the regulation of the proneural AS‐C genes and the neurogenic genes of the Enhancer of split complex. In this paper we report the identification of a transcript associated with the vnd locus, the transcript distribution in embryogenesis, which is compatible with the nervous system mutant phenotypes described for this gene, and that the protein product is a member of the NK‐2 homeodomain family. We discuss these findings within the framework of early Drosophila neurogenesis and the known phenotypes associated with the vnd locus.

Dorsoventral patterning in the Drosophila central nervous system: the vnd homeobox gene specifies ventral column identity

“…1C-F). During these stages, the Vnd protein pattern is identical to the vnd RNA pattern (Jimé nez et al 1995;Mellerick and Nirenberg 1995) except that there is a slight lag between the time of transcription and translation. At stage 11 and later, Vnd protein is detected in a complex pattern of neurons including some, but not all, of the neuronal progeny of the ventral column neuroblasts.…”

“…ventral nervous system defective (vnd) is an NK-2 homeobox gene expressed in the ventral column of neuroectoderm and neuroblasts (Jimé nez et al 1995;Mellerick and Nirenberg 1995). vnd is required to activate proneural gene expression in a subset of the ventral column neuroectoderm and neuroblasts (Skeath et al 1994), and for the formation of a subset of ventral and intermediate column neuroblasts (Jimé nez and Campos-Ortega 1990; Skeath et al 1994).…”

Mutations that affect the ability of the vnd/NK-2 homeoprotein to regulate gene expression: Transgenic alterations and tertiary structure

“…Among the homeobox genes, members of the NK family are of particular interest because they are expressed in neuroectodermal cells (5) and are associated with the development of vital organs (6,7) such as the heart, lung, prostate, or thyroid, or with the formation of part of the CNS (8). Within the NK family of homeobox genes, the NK-2 class, whose founding member is vnd͞NK-2 from Drosophila melanogaster (8)(9)(10), is defined by the presence of tyrosine in position 54 of the homeodomain (11,12).…”

“…Within the NK family of homeobox genes, the NK-2 class, whose founding member is vnd͞NK-2 from Drosophila melanogaster (8)(9)(10), is defined by the presence of tyrosine in position 54 of the homeodomain (11,12). This tyrosine is the major determinant of the nucleotide-binding specificity (13,14) to a sequence of DNA that contains 5Ј-CAAGTG-3Ј as its core (15)(16)(17)(18) through direct interaction between the side chain of Y54 and the cytosine that complements the guanine (in bold) of the consensus DNA (14).…”

“…Many homeobox genes in the NK-2 class are essential for proper development during embryogenesis (6)(7)(8)(21)(22)(23) for many species, including humans. The vnd͞NK-2 gene of Dro-sophila is expressed in ventral neuroectodermal cells and then in ventral neuroblasts whose progeny give rise to part of the ventral nerve cord (8,24).…”