Genetic Dissection of itpr Gene Function Reveals a Vital Requirement in Aminergic Cells of Drosophila Larvae

Abstract

Signaling by the second messenger inositol 1,4,5-trisphosphate is thought to affect several developmental and physiological processes. Mutants in the inositol 1,4,5-trisphosphate receptor (itpr) gene of Drosophila exhibit delays in molting while stronger alleles are also larval lethal. In a freshly generated set of EMS alleles for the itpr locus we have sequenced and identified single point mutations in seven mutant chromosomes. The predicted allelic strength of these mutants matches the observed levels of lethality. They range from weak hypomorphs to complete nulls. Interestingly, lethality in three heteroallelic combinations has a component of cold sensitivity. The temporal focus of cold sensitivity lies in the larval stages, predominantly at second instar. Coupled with our earlier observation that an itpr homozygous null allele dies at the second instar stage, it appears that there is a critical period for itpr gene function in second instar larvae. Here we show that the focus of this critical function lies in aminergic cells by rescue with UAS-itpr and DdC GAL4. However, this function does not require synaptic activity, suggesting that InsP 3 -mediated Ca 2ϩ release regulates the neurohormonal action of serotonin.

Inositol 1,4,5-Trisphosphate Receptor and dSTIM Function inDrosophilaInsulin-Producing Neurons Regulates Systemic Intracellular Calcium Homeostasis and Flight

“…itpr ka1091/ug3 and itpr wc703/ug3 are heteroallelic combinations of single point mutants in the itpr gene that were generated in an EMS (ethyl methanesulfonate) screen. Detailed molecular information on these alleles has been published (Joshi et al, 2004). The UASdSTIM ϩ transgenic strain on chromosome 2 was generated by injecting embryos using a standard Drosophila embryo microinjection protocol with a pUASTdSTIM construct.…”

“…؉ function in DILP2 neurons rescues flight defects of itpr mutants Expression of the wild-type Drosophila InsP 3 R cDNA (UASitpr ϩ ) in the aminergic domain can rescue both larval and adult phenotypes of itpr mutants (Banerjee et al, 2004;Joshi et al, 2004). Larval itpr mutant phenotypes of growth, feeding and viability can also be rescued to a significant extent by itpr ϩ expression in the DILP2 neurons (Agrawal et al, 2009).…”

Reduced Odor Responses from Antennal Neurons of Gqα, Phospholipase Cβ, andrdgAMutants inDrosophilaSupport a Role for a Phospholipid Intermediate in Insect Olfactory Transduction

“…itpr sv35 is a null (Joshi et al, 2004), whereas itpr ka901 can act as a gain-of-function allele . The effect of these alleles on antennal olfactory responses has not been investigated before.…”

Loss of Flight and Associated Neuronal Rhythmicity in Inositol 1,4,5-Trisphosphate Receptor Mutants ofDrosophila

“…These studies demonstrate the relevance of InsP 3 signaling in modulating complex adult behaviors and also underline the importance of generating mutant alleles that can be studied as adults. Toward this end, we generated a set of point mutant alleles for the InsP 3 R gene (itpr) in Drosophila, some of which are viable as heteroallelic combinations (Deshpande et al, 2000;Joshi et al, 2004). Their viability is very likely attributable to compensatory effects among different mutant monomers, enabling assembly of a functional tetrameric form of the InsP 3 R (Maeda et al, 1991;Serysheva et al, 2003).…”