Down-Regulation of Inpp5e Associated With Abnormal Ciliogenesis During Embryonic Neurodevelopment Under Inositol Deficiency

Abstract

The inositol polyphosphate-5-phosphatase E (Inpp5e) gene is located on chromosome 9q34.3. The enzyme it encodes mainly hydrolyzes the 5-phosphate groups of phosphatidylinositol (3,4,5)-trisphosphate (PtdIns (3,4,5) P3) and phosphatidylinositol (4,5)-bisphosphate (PtdIns (4,5)P2), which are closely related to ciliogenesis and embryonic neurodevelopment, through mechanisms that are largely unknown. Here we studied the role of Inpp5e gene in ciliogenesis during embryonic neurodevelopment using inositol-deficiency neural tube defects (NTDs) mouse and cell models. Confocal microscopy and scanning electron microscope were used to examine the number and the length of primary cilia. The dynamic changes of Inpp5e expression in embryonic murine brain tissues were observed during Embryonic Day 10.5–13.5 (E 10.5–13.5). Immunohistochemistry, western blot, polymerase chain reaction (PCR) arrays were applied to detect the expression of Inpp5e and cilia-related genes of the embryonic brain tissues in inositol deficiency NTDs mouse. Real-time quantitative PCR (RT-qPCR) was used to validate the candidate genes in cell models. The levels of inositol and PtdIns(3,4) P2 were measured using gas chromatography-mass spectrometry (GC-MS) and enzyme linked immunosorbent assay (ELISA), respectively. Our results showed that the expression levels of Inpp5e gradually decreased in the forebrain tissues of the control embryos, but no stable trend was observed in the inositol deficiency NTDs embryos. Inpp5e expression in inositol deficiency NTDs embryos was significantly decreased compared with the control tissues. The expression levels of Inpp5e gene and the PtdIns (3,4) P2 levels were also significantly decreased in the inositol deficient cell model. A reduced number and length of primary cilia were observed in NIH3T3 cells when inositol deficient. Three important cilia-related genes (Ift80, Mkks, Smo) were down-regulated significantly in the inositol-deficient NTDs mouse and cell models, and Smo was highly involved in NTDs. In summary, these findings suggested that down-regulation of Inpp5e might be associated with abnormal ciliogenesis during embryonic neurodevelopment, under conditions of inositol deficiency.

BMP/Smad Pathway Is Involved in Lithium Carbonate-Induced Neural-Tube Defects in Mice and Neural Stem Cells

“…Although no obvious phenotypic abnormalities were found under the dissecting microscope, in the Li 2 CO 3 -treated nonmalformation group, HE staining showed a narrower ventricular cavity of the hindbrain and midbrain, compared to that of the control group ( Figure 1 c). These results are consistent with our previous study [ 16 , 35 ]. The process of neural-tube closure was disrupted by maternal Li 2 CO 3 exposure during embryonic development.…”

Multiple ciliary localization signals control INPP5E ciliary targeting

“…The complexity and redundancy in INPP5E ciliary targeting suggest this is an important process, subject to fine regulation. This is consistent with the surprisingly wide range of functions INPP5E plays at the cilium, controlling among others their lipid and protein composition, assembly and disassembly, exovesicle release, and signaling ( Jacoby et al, 2009 ; Bielas et al, 2009 ; Guo et al, 2019 ; Garcia-Gonzalo et al, 2015 ; Chávez et al, 2015 ; Badgandi et al, 2017 ; Dyson et al, 2017 ; Phua et al, 2017 ; Wang et al, 2011 ; Hakim et al, 2016 ; Xu et al, 2016 ; Xu et al, 2017 ; Constable et al, 2020 ; Hasenpusch-Theil et al, 2020 ; Sharif et al, 2021 ; Ukhanov et al, 2022 ; Yue et al, 2021 ). With the broader view of INPP5E ciliary targeting provided herein, the stage is now set for a deeper molecular understanding of these processes and their regulation.…”

“…INPP5E plays multiple important roles at the cilium. Among others, these roles include regulation of: (i) ciliary phosphoinositide levels, (ii) ciliary protein composition, (iii) ciliary Hedgehog and PI3K signaling, (iv) ciliary ectovesicle release, (v) ciliary stability, and (vi) ciliogenesis ( Jacoby et al, 2009 ; Bielas et al, 2009 ; Guo et al, 2019 ; Garcia-Gonzalo et al, 2015 ; Chávez et al, 2015 ; Badgandi et al, 2017 ; Dyson et al, 2017 ; Phua et al, 2017 ; Wang et al, 2011 ; Hakim et al, 2016 ; Xu et al, 2016 ; Xu et al, 2017 ; Constable et al, 2020 ; Hasenpusch-Theil et al, 2020 ; Sharif et al, 2021 ; Ukhanov et al, 2022 ; Yue et al, 2021 ). Although most of its functions are ciliary, INPP5E also plays extraciliary roles, like promoting autophagosome-lysosome fusion during autophagy ( Hasegawa et al, 2016 ).…”

Multiple Ciliary Localization Signals Control INPP5E Ciliary Targeting

“…The complexity and redundancy in INPP5E ciliary targeting suggest this is a very important process, subject to fine regulation. This is consistent with the surprisingly wide range of functions INPP5E plays at the cilium, controlling among others their lipid and protein composition, assembly and disassembly, exovesicle release, and signaling 7,8,12,[32][33][34][35][36][37][38][39][40][41][42][43][44][45] . By providing a much broader view of the…”

“…INPP5E plays multiple important roles at the cilium. Among others, these roles include regulation of: (i) ciliary phosphoinositide levels, (ii) ciliary protein composition, (iii) ciliary Hedgehog and PI3K signaling, (iv) ciliary ectovesicle release, (v) ciliary stability, and (vi) ciliogenesis 7,8,12,[32][33][34][35][36][37][38][39][40][41][42][43][44][45] . Although most of its functions are ciliary, INPP5E also plays extraciliary roles, like promoting autophagosomelysosome fusion during autophagy 46 .…”