Proviral insertions in the zebrafish hagoromo gene, encoding an F-box/WD40-repeat protein, cause stripe pattern anomalies

Abstract

The zebrafish, Danio rerio, has three types of pigment cells (melanophores, xanthophores and iridophores) and, in adult fish, these cells are organized into a stripe pattern. The mechanisms underlying formation of the stripe pattern are largely unknown. We report here the identification and characterization of a novel dominant zebrafish mutation, hagoromo (hag), which was generated by insertional mutagenesis using a pseudotyped retrovirus. The hag mutation caused disorganized stripe patterns. Two hag mutant alleles were isolated independently and proviruses were located within the fifth intron of a novel gene, which we named hag, encoding an F-box/WD40-repeat protein. The hag gene was mapped to linkage group (LG)13, close to fgf8 and pax2.1. Amino acid sequence similarity, conserved exon-intron boundaries and conserved synteny indicated that zebrafish hag is an ortholog of mouse Dactylin, the gene mutated in the Dactylaplasia (Dac) mouse [1]. The Dac mutation is dominant and causes defects in digit formation in fore- and hindlimbs. This study revealed that the hag locus is important for pattern formation in fish but is involved in distinct morphogenetic events in different vertebrates.

The complexity of alternative splicing of hagoromo mRNAs is increased in an explosively speciated lineage in East African cichlids

“…The e9terminal types included e9terminal-fl that contained nine exons and resembled the zebrafish cDNA (17) [ (1) Because a hag cDNA probe containing exons 2 and 3 hybridized to a single band on a genomic Southern blot (see Fig. 5, which is published as supporting information on the PNAS web site, www.pnas.org), we concluded that these various subtypes of mRNA were generated from a single hag gene by alternative splicing by intron retention and͞or exon skipping.…”

“…The antisense probe can potentially hybridize to all hag transcripts. In zebrafish, expression of the hag gene is ubiquitous during all stages of development and in almost all adult tissues (17). The expression of hag was detected in a skin sample from a whole-body skin preparation from Haplochromis sp.…”

“…2d), suggesting that the cichlid hag gene is indeed involved in pigmentation. The product of the hag gene is a member of the family of F-box͞ WD-repeat proteins in which the F-box and WD-repeats are fused (17). The proteins in the F-box͞WD-repeat family function in a variety of regulatory pathways including cell division control (21,22), sulfur metabolism (23), and differentiation (24).…”

“…In zebrafish, various mutations affecting pigmentation have been described (13,14), and some relevant genes have been cloned and characterized (e.g., sparse, nacre, and hagoromo; refs. [15][16][17].…”

“…With insertional mutagenesis, the zebrafish gene hagoromo (hag) was shown to be responsible for pigment pattern formation (17). Recently, we cloned a cichlid homolog of hag and showed a correlation between the morphological diversity of the Great Lakes lineage and the evolutionary rate of amino acid sequence changes in the hag gene (18).…”