ABSTRACT
INTRODUCTION: Progesterone (P4 ) and its product, 5α-pregnan-3α-ol-20-one (3α,5α-THP), act in the midbrain ventral tegmental area (VTA) to alter motivated behaviors, such as mating, and motor and anxiety behavior. Of interest is whether 3α,5α-THP formation requires the pregnane xenobiotic receptor (PXR), which is expressed in the midbrain of rats. AIM: The role of PXR in the midbrain for 3α,5α-THP formation, which precedes modulation of motivated behaviors, was investigated. METHODS: Rats had estrous cycle phase determined and were assessed when they were in diestrus or proestrus. Diestrous and proestrous rats were infused with control or antisense oligodeoxyribonucleotides (AS-ODNs) targeted against PXR to the VTA. MAIN OUTCOME MEASURES: In pilot studies, PXR gene and protein expression in the midbrain were determined with quantitative reverse transcriptase polymerase chain reaction and Western blotting, respectively. Diestrous and proestrous rats infused with control or AS-ODNs to the VTA were tested for anxiety (open field and plus maze), social (social interaction), and sexual (paced mating) behavior. Expression of PXR in the midbrain was verified with Western blotting. Plasma estradiol, P4 , dihydroprogesterone (DHP), and 3α,5α-THP levels, and brain P4 , DHP, and 3α,5α-THP levels were measured. We predicted that proestrous rats infused with PXR AS-ODNs would have decreased anti-anxiety, social, and sexual behavior, lower midbrain expression of PXR, and lower midbrain levels of 3α,5α-THP compared with controls. RESULTS: Results supported the hypothesis that formation of 3α,5α-THP requires PXR and may be important for motivated behaviors. PXR AS-ODN, compared with control, infusions to the VTA reduced PXR expression and 3α,5α-THP levels in the midbrain and attenuated sexual receptivity of proestrous rats. CONCLUSIONS: Knockdown of PXR in the midbrain reduces 3α,5α-THP levels and sexual receptivity of proestrous rats. Thus, PXR in the midbrain may be required for the observed increase in 3α-5α-THP during proestrus, which has subsequent effects on motivated, reproductive behaviors.
Subject(s)
Mesencephalon/metabolism , Motivation , Pregnanolone/metabolism , Proestrus/metabolism , Receptors, Steroid/metabolism , Reproduction , Sexual Behavior, Animal , Animals , Anxiety/metabolism , Estradiol/blood , Estradiol/metabolism , Female , Gene Knockdown Techniques , Interpersonal Relations , Male , Pregnane X Receptor , Pregnanolone/blood , Proestrus/blood , Progesterone/blood , Progesterone/metabolism , Rats , Rats, Long-Evans , Receptors, Steroid/genetics , Ventral Tegmental Area/metabolismABSTRACT
We report the identification and characterization of expression of a new gene in Drosophila, which we have named Mrityu (Mri). Mri was initially isolated in a microarray screen to identify molecules regulated by the transcription factor klumpfuss during retinal apoptosis. The amino acid sequence of Mri contains a BTB/POZ domain with homologues across the animal kingdom. Mri transcripts are present at every developmental stage as assayed by RT-PCR. We show expression of Mri transcripts in the female germline, confined to the nurse cells, beginning at stage 7/8. During embryonic development Mri is uniformly expressed early and then is refined to the gut and mesoderm primordia while expression decreases in the ectoderm. In the retina Mri is again expressed uniformly early, i.e., in the third instar larva and becomes more refined during pupal development where the transcripts is dynamically expressed in the cone cells and primary, secondary and tertiary pigment cells.
Subject(s)
Drosophila Proteins/chemistry , Drosophila Proteins/metabolism , Drosophila/chemistry , Drosophila/embryology , Gene Expression Regulation, Developmental , Glycerol Kinase/chemistry , Glycerol Kinase/metabolism , Animals , Drosophila Proteins/genetics , Embryo, Nonmammalian , Fluorescent Antibody Technique, Direct , Glycerol Kinase/genetics , In Situ Hybridization , Protein Structure, Tertiary , RNA, Messenger/metabolism , Retina/chemistry , Retina/embryology , Retina/metabolism , Reverse Transcriptase Polymerase Chain Reaction , Tissue DistributionABSTRACT
Programmed cell death (PCD) plays a central role in the sculpting and maturation of developing epithelia. In adult tissue, PCD plays a further role in the prevention of malignancy though removal of damaged cells. Here, we report that mutations in klumpfuss result in an excess of support cells during maturation of the developing Drosophila pupal retina. These ectopic cells are the result of a partial and specific failure of apoptotic death during normal cell fate selection. klumpfuss is required and differentially expressed in the cells that choose the life or death cell fate. We also provide genetic and biochemical evidence that klumpfuss regulates this process through down-regulation of the Epidermal Growth Factor Receptor/dRas1 signaling pathway. Based on its sequence Klumpfuss is an EGR-class nuclear factor, and our results suggest a mechanism by which mutations in EGR-class factors such as Wilms' Tumor Suppressor-1 may result in oncogenic events such as pediatric kidney tumors.
