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Novel function of PIWIL1 in neuronal polarization and migration via regulation of microtubule-associated proteins.

Zhao PP, Yao MJ, Chang SY, Gou LT, Liu MF, Qiu ZL, Yuan XB - Mol Brain (2015)

Bottom Line: Furthermore, we found that PIWIL1 unexpectedly regulates the expression of microtubule-associated proteins in cortical neurons.PIWIL1 regulates neuronal polarization and radial migration partly via modulating the expression of microtubule-associated proteins (MAPs).Our finding of PIWIL1's function in neuronal development implies conserved functions of molecules participating in morphogenesis of brain and germline tissue and provides a mechanism as to how mutations of PIWI may be associated with autism.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200031, China.

ABSTRACT

Background: Young neurons in the developing brain establish a polarized morphology for proper migration. The PIWI family of piRNA processing proteins are considered to be restrictively expressed in germline tissues and several types of cancer cells. They play important roles in spermatogenesis, stem cell maintenance, piRNA biogenesis, and transposon silencing. Interestingly a recent study showed that de novo mutations of PIWI family members are strongly associated with autism.

Results: Here, we report that PIWI-like 1 (PIWIL1), a PIWI family member known to be essential for the transition of round spermatid into elongated spermatid, plays a role in the polarization and radial migration of newborn neurons in the developing cerebral cortex. Knocking down PIWIL1 in newborn cortical neurons by in utero electroporation of specific siRNAs resulted in retardation of the transition of neurons from the multipolar stage to the bipolar stage followed by a defect in their radial migration to the proper destination. Domain analysis showed that both the RNA binding PAZ domain and the RNA processing PIWI domain in PIWIL1 were indispensable for its function in neuronal migration. Furthermore, we found that PIWIL1 unexpectedly regulates the expression of microtubule-associated proteins in cortical neurons.

Conclusions: PIWIL1 regulates neuronal polarization and radial migration partly via modulating the expression of microtubule-associated proteins (MAPs). Our finding of PIWIL1's function in neuronal development implies conserved functions of molecules participating in morphogenesis of brain and germline tissue and provides a mechanism as to how mutations of PIWI may be associated with autism.

No MeSH data available.


Related in: MedlinePlus

PIWIL1 knockdown impairs polarization of cortical neurons ex vivo. a Diagram of the ex vivo assay. b, c Average numbers of primary neurites of electroporated cells. d Immunostaining: cultured neurons with PIWIL1 knockdown exhibited multipolar morphology and lower levels of Tau but not Tuj1. e Average neurites’ fluorescence intensity of Tau in GFP+ neurons. Scale bar, 20 μm. Error bar, SEM, *P < 0.05, ***P < 0.001 (Student’s t-test)
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Fig3: PIWIL1 knockdown impairs polarization of cortical neurons ex vivo. a Diagram of the ex vivo assay. b, c Average numbers of primary neurites of electroporated cells. d Immunostaining: cultured neurons with PIWIL1 knockdown exhibited multipolar morphology and lower levels of Tau but not Tuj1. e Average neurites’ fluorescence intensity of Tau in GFP+ neurons. Scale bar, 20 μm. Error bar, SEM, *P < 0.05, ***P < 0.001 (Student’s t-test)

Mentions: We further analyzed the effect of PIWI knockdown on neuronal morphology using an ex vivo assay, in which newborn neurons derived from electroporated brains were dissociated and cultured for 2 days before morphological analysis (Fig. 3a). We found that neurons with PIWIL1 knockdown showed a multipolar morphology and significantly larger number of primary neurites than that of control neurons (Fig. 3b and c). By labeling the axon with immunostaining of Tau, we observed that neurons in PIWIL1 RNAi group didn’t have a specific axon and unexpectedly showed reduced expression of Tau after 2 days of culture (Fig. 3d). After quantification of the fluorescence intensity, we observed that average fluorescence intensity of Tau staining at the neurite of GFP positive neurons in the RNAi group was significantly lower than that of the control group (Fig. 3e). In contrast, the expression of the pan-neuronal marker Tuj1 was not affected. Taken together, the above results show that PIWIL1 promotes the multipolar–bipolar transition of newborn neurons, which is essential for the proper radial migration of cortical neurons.Fig. 3


Novel function of PIWIL1 in neuronal polarization and migration via regulation of microtubule-associated proteins.

Zhao PP, Yao MJ, Chang SY, Gou LT, Liu MF, Qiu ZL, Yuan XB - Mol Brain (2015)

PIWIL1 knockdown impairs polarization of cortical neurons ex vivo. a Diagram of the ex vivo assay. b, c Average numbers of primary neurites of electroporated cells. d Immunostaining: cultured neurons with PIWIL1 knockdown exhibited multipolar morphology and lower levels of Tau but not Tuj1. e Average neurites’ fluorescence intensity of Tau in GFP+ neurons. Scale bar, 20 μm. Error bar, SEM, *P < 0.05, ***P < 0.001 (Student’s t-test)
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4477296&req=5

Fig3: PIWIL1 knockdown impairs polarization of cortical neurons ex vivo. a Diagram of the ex vivo assay. b, c Average numbers of primary neurites of electroporated cells. d Immunostaining: cultured neurons with PIWIL1 knockdown exhibited multipolar morphology and lower levels of Tau but not Tuj1. e Average neurites’ fluorescence intensity of Tau in GFP+ neurons. Scale bar, 20 μm. Error bar, SEM, *P < 0.05, ***P < 0.001 (Student’s t-test)
Mentions: We further analyzed the effect of PIWI knockdown on neuronal morphology using an ex vivo assay, in which newborn neurons derived from electroporated brains were dissociated and cultured for 2 days before morphological analysis (Fig. 3a). We found that neurons with PIWIL1 knockdown showed a multipolar morphology and significantly larger number of primary neurites than that of control neurons (Fig. 3b and c). By labeling the axon with immunostaining of Tau, we observed that neurons in PIWIL1 RNAi group didn’t have a specific axon and unexpectedly showed reduced expression of Tau after 2 days of culture (Fig. 3d). After quantification of the fluorescence intensity, we observed that average fluorescence intensity of Tau staining at the neurite of GFP positive neurons in the RNAi group was significantly lower than that of the control group (Fig. 3e). In contrast, the expression of the pan-neuronal marker Tuj1 was not affected. Taken together, the above results show that PIWIL1 promotes the multipolar–bipolar transition of newborn neurons, which is essential for the proper radial migration of cortical neurons.Fig. 3

Bottom Line: Furthermore, we found that PIWIL1 unexpectedly regulates the expression of microtubule-associated proteins in cortical neurons.PIWIL1 regulates neuronal polarization and radial migration partly via modulating the expression of microtubule-associated proteins (MAPs).Our finding of PIWIL1's function in neuronal development implies conserved functions of molecules participating in morphogenesis of brain and germline tissue and provides a mechanism as to how mutations of PIWI may be associated with autism.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200031, China.

ABSTRACT

Background: Young neurons in the developing brain establish a polarized morphology for proper migration. The PIWI family of piRNA processing proteins are considered to be restrictively expressed in germline tissues and several types of cancer cells. They play important roles in spermatogenesis, stem cell maintenance, piRNA biogenesis, and transposon silencing. Interestingly a recent study showed that de novo mutations of PIWI family members are strongly associated with autism.

Results: Here, we report that PIWI-like 1 (PIWIL1), a PIWI family member known to be essential for the transition of round spermatid into elongated spermatid, plays a role in the polarization and radial migration of newborn neurons in the developing cerebral cortex. Knocking down PIWIL1 in newborn cortical neurons by in utero electroporation of specific siRNAs resulted in retardation of the transition of neurons from the multipolar stage to the bipolar stage followed by a defect in their radial migration to the proper destination. Domain analysis showed that both the RNA binding PAZ domain and the RNA processing PIWI domain in PIWIL1 were indispensable for its function in neuronal migration. Furthermore, we found that PIWIL1 unexpectedly regulates the expression of microtubule-associated proteins in cortical neurons.

Conclusions: PIWIL1 regulates neuronal polarization and radial migration partly via modulating the expression of microtubule-associated proteins (MAPs). Our finding of PIWIL1's function in neuronal development implies conserved functions of molecules participating in morphogenesis of brain and germline tissue and provides a mechanism as to how mutations of PIWI may be associated with autism.

No MeSH data available.


Related in: MedlinePlus