Mutation of Drosophila Lsd1 Disrupts H3-K4 Methylation, Resulting in Tissue-Specific Defects during Development

Abstract

Histone-tail modifications play a fundamental role in the processes that establish chromatin structure and determine gene expression. One such modification, histone methylation, was considered irreversible until the recent discovery of histone demethylases. Lsd1 was the first histone demethylase to be identified. Lsd1 is highly conserved in many species, from yeast to humans, but its function has primarily been studied through biochemical approaches. The mammalian ortholog has been shown to demethylate monomethyl- and dimethyl-K4 and -K9 residues of histone H3. Here we describe the effects of Lsd1 mutation in Drosophila. The inactivation of dLsd1 strongly affects the global level of monomethyl- and dimethyl-H3-K4 methylation and results in elevated expression of a subset of genes. dLsd1 is not an essential gene, but animal viability is strongly reduced in mutant animals in a gender-specific manner. Interestingly, dLsd1 mutants are sterile and possess defects in ovary development, indicating that dLsd1 has tissue-specific functions. Mutant alleles of dLsd1 suppress positional-effect variegation, suggesting a disruption of the balance between euchromatin and heterochromatin. Taken together, these results show that dLsd1-mediated H3-K4 demethylation has a significant and specific role in Drosophila development.

Mechanisms involved in the regulation of histone lysine demethylases

“…The mammalian KDM1/LSD1 shows relatively higher levels of expression in mouse testis and related tissues, complementing the observed lower levels of H3K4me2 in these tissues [4]. Mutations of the fly KDM1 homolog lead to sex-specific embryonic lethality and sterility in the surviving (primarily female) offspring, likely due to defects in ovary development [5]. H3K4me2 levels are higher in the primordial germ cells of heterozygous females and the fly KDM1 protein has in vitro demethylase activity for H3K4me2/1 [6], supporting a conservation of enzymatic specificity between mammal and fly.…”

Functional antagonism between histone H3K4 demethylases in vivo

“…Homozygous mutation of dLsd1 leads to a held-out wing phenotype, male lethality, and defects in oogenesis (Di Stefano et al 2007). Further analysis of dLsd1 DN mutant flies revealed an additional defect in the wing.…”

“…1A-D; Table 1). To determine whether this suppression was limited to the wing, we tested the Lid mutant allele for its ability to modify the highly penetrant dLsd1 DN oogenesis defect (Di Stefano et al 2007). To gain insights into the specific effects of Lid mutation on the dLsd1 DN -dependent oogenesis defect, wild-type and mutant ovaries were stained with antibodies specific for ovarian cell markers.…”

“…Like its mammalian counterpart, dLsd1 specifically demethylates H3K4me2 and H3K4me1 residues, indicating functional conservation (Rudolph et al 2007). We showed that dLsd1 mutation affects male viability as well as specific developmental processes such as wing development and oogenesis (Di Stefano et al 2007). Furthermore, mutant alleles of dLsd1 strongly suppress positional effect variegation (PEV), indicating that dLsd1 contributes to maintaining the balance between euchromatin and heterochromatin (Di Stefano et al 2007;Rudolph et al 2007).…”

“…We showed that dLsd1 mutation affects male viability as well as specific developmental processes such as wing development and oogenesis (Di Stefano et al 2007). Furthermore, mutant alleles of dLsd1 strongly suppress positional effect variegation (PEV), indicating that dLsd1 contributes to maintaining the balance between euchromatin and heterochromatin (Di Stefano et al 2007;Rudolph et al 2007). Taken together, these studies showed that dLsd1 plays a crucial role in chromatin regulation during Drosophila development, and that its depletion impacts specific developmental processes.…”