Disruption ofINOS, a Gene Encodingmyo-Inositol Phosphate Synthase, Causes Male Sterility inDrosophila melanogaster

Abstract

Inositol is a precursor for the phospholipid membrane component phosphatidylinositol (PI), involved in signal transduction pathways, endoplasmic reticulum stress, and osmoregulation. Alterations of inositol metabolism have been implicated in human reproductive issues, the therapeutic effects of drugs used to treat epilepsy and bipolar disorder, spinal cord defects, and diseases including diabetes and Alzheimer’s. The sole known inositol synthetic enzyme is myo-inositol synthase (MIPS), and the homolog in Drosophilia melanogaster is encoded by the Inos gene. Three identical deletion strains (inosΔDF/CyO) were constructed, confirmed by PCR and sequencing, and homozygotes (inosΔDF/inosΔDF) were shown to lack the transcript encoding the MIPS enzyme. Without inositol, homozygous inosΔDF deletion fertilized eggs develop only to the first-instar larval stage. When transferred as pupae to food without inositol, however, inosΔDF homozygotes die significantly sooner than wild-type flies. Even with dietary inositol the homozygous inosΔDF males are sterile. An inos allele, with a P-element inserted into the first intron, fails to complement this male sterile phenotype. An additional copy of the Inos gene inserted into another chromosome rescues all the phenotypes. These genetic and phenotypic analyses establish D. melanogaster as an excellent model organism in which to examine the role of inositol synthesis in development and reproduction.

Regulated inositol synthesis is critical for balanced metabolism and development in Drosophila melanogaster

“…All fly stocks were grown on either rich food (BDSC cornmeal food, ) or modified semi-defined food (per liter 10 g agar (ThermoFisher Scientific), 80 g brewers yeast (Genesee), 20 g yeast extract (ThermoFisher Scientific), 20 g peptone (ThermoFisher Scientific), sucrose (ThermoFisher Scientific) as indicated, Musselman et al, 2011 ) with or without 50 µM inositol (Sigma-Aldrich) as indicated (this concentration is sufficient to support growth of a homozygous Inos deletion mutant (inos ΔDF /inos ΔDF ), Jackson et al, 2018 ).…”

“…In contrast, diseases of brain development and dysfunction are associated with elevated levels of inositol and some are treated by pharmacological agents that reduce the inositol levels ( Yu et al, 2017 ; Case et al, 2018 ; Patkee et al, 2021 ). Drosophila melanogaster (fruit fly) was established as a model to study inositol metabolism with a demonstration of its essential role in spermatogenesis ( Jackson et al, 2018 ). This study examines the regulation of inositol synthesis in animals, and its role in metabolism and development in D. melanogaster .…”

Inositol synthesis gene is required for circadian rhythm ofDrosophila melanogastermating behavior

“…Furthermore, fission yeast requires Myo -inositol for mating and sporulation (Niederberger et al, 1998; Voicu et al, 2002). In D. melanogaster , disruption of Inos gene causes male sterility (Jackson, Flores, Eldon, & Klig, 2018). Furthermore, Inos is highly expressed in testes and the head in D. melanogaster (Chen et al, 2014).…”

Inositol in Disease and Development: Roles of Catabolism via myo-Inositol Oxygenase in Drosophila melanogaster

“…Flies were maintained in standard laboratory conditions at 25 °C and 70–80% humidity on a 12 h:12 h light–dark cycle. All fly stocks were grown on either rich food (BDSC cornmeal food, (accessed on 29 April 2011)) or modified food (per liter, 10 g of agar (Fisher Scientific, Waltham, MA, USA), 80 g of brewer’s yeast (Genesee), 20 g of yeast extract (Fisher Scientific), 20 g of peptone (Fisher Scientific), and sucrose (Fisher Scientific) as indicated, [ 49 ]) with or without 50 µM of myo- inositol (Sigma, St. Louis, MO, USA) as indicated, which is sufficient to support growth of a homozygous Inos deletion mutant (inos ΔDF /inos ΔDF ) [ 16 ]. Semi-defined food (casamino acids sucrose (CAA-S) and casamino acids myo- inositol (CAA-I)) was prepared essentially as described [ 82 ] with modifications [ 83 ].…”

“…Rats with upregulated myo- inositol catabolism have increased blood glucose and related pathobiological stress [ 13 , 14 , 15 ]. In the fruit fly, Drosophila melanogaster, reduced myo- inositol synthesis was shown to cause defective spermatogenesis [ 16 ], and increased myo- inositol synthesis caused severe developmental defects [ 17 ]. This led to the current study investigating the role of myo- inositol catabolism in fruit fly development and metabolism.…”