Functional genomic analysis of the 61D-61F region of the third chromosome ofDrosophila melanogaster

Abstract

Assigning functional significance to completed genome sequences is one of the next challenges in biological science. Conventional genetic tools such as deficiency chromosomes help assign essential complementation groups to their corresponding genes. We describe an F2 genetic screen to identify lethal mutations within cytogenetic region 61D-61F of the third chromosome of Drosophila melanogaster. One hundred sixteen mutations were identified by their failure to complement both Df(3L)bab-PG and Df(3L)3C7. These alleles were assigned to 14 complementation groups and 9 deficiency intervals. Complementation groups were ordered using existing deficiencies, as well as new deficiencies generated in this study. With the aid of the genomic sequence, genetic and physical maps in the region were correlated by use of PCR to localize the breakpoints of deficiencies within a 268-kb genomic contig (GenBank accession No. AC005847). Six essential complementation groups were assigned to specific genes, including genes encoding a porphobilinogen deaminase and a Sac1-like protein.

Sac1, a lipid phosphatase at the interface of vesicular and nonvesicular transport

“…Rat and mouse Sac1 proteins are ubiquitously expressed in adult and embryonic tissues, with highest expression in Purkinje cells, have 35% sequence identity with yeast Sac1 and are also enriched at ER and Golgi membranes . Drosophila Sac1 is expressed in all tissues and stages of development, shows 47% identity with mammalian Sac1, and associates with ER and Golgi membranes . Human Sac1 shares 32% and 95% identity with yeast and rat Sac1, respectively, and is also present at ER and Golgi membranes .…”

“…The first mutations in Drosophila sac1 were isolated in a screen for essential genes in the 61D‐61F region of chromosome III . sac1 null mutant flies die as embryos due to defects in DC .…”

“…30,31 Drosophila Sac1 is expressed in all tissues and stages of development, shows 47% identity with mammalian Sac1, and associates with ER and Golgi membranes. [32][33][34] Human Sac1 shares 32% and 95% identity with yeast and rat Sac1, respectively, and is also present at ER and Golgi membranes. 35 Notably, ectopic expression of rat, mouse or human Sac1 complements phenotypes associated with loss of yeast Sac1, including effects on PIP levels, inositol auxotrophy and cold sensitivity.…”

“…The first mutations in Drosophila sac1 were isolated in a screen for essential genes in the 61D-61F region of chromosome III. 33,36 sac1 null mutant flies die as embryos due to defects in DC. 36 JNK3 during neuronal stress, 98 it is tempting to speculate that Sac1 and JNK might act in a mutually antagonistic manner such that normal Sac1 activity at the ER reduces JNK signaling, whereas stressdependent JNK activation inhibits Sac1 activity at the ER.…”

The phosphoinositide phosphatase Sac1 regulates cell shape and microtubule stability in the developing Drosophila eye

“…We previously showed that Sac1 is required for normal eye development in Drosophila (Wei et al, 2003b). Sac1 is essential for viability in Drosophila (Wei et al, 2003a,b).…”