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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 affects neuronal migration through regulating the expression of MAPs. a, b MAP2 levels (bands indicated by the arrow) were significantly decreased in the cortical tissue of adult PIWIL1-knockout mice (tissues were all from male animals). Statistics analysis was based on 4 technical repeats on pooled samples (n = 2). c Cortex of PIWIL1-knockout mice showed lower level of MAP2 immunofluorescence signal (red arrows indicate MAP2 signal in WT brain). Scale bar, 20 μm. d, e Co-electroporation of MAP2B with PIWIL1 siRNA largely attenuated the migration defect in mouse brains. Scramble vs RNAi 2; RNAi 2 + CAG vs RNAi 2 + MAP2B. Scale bar, 150 μm. Error bar, SEM, *P < 0.05, **P < 0.01, ***P < 0.001 (Student’s t-test)
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Fig5: PIWIL1 affects neuronal migration through regulating the expression of MAPs. a, b MAP2 levels (bands indicated by the arrow) were significantly decreased in the cortical tissue of adult PIWIL1-knockout mice (tissues were all from male animals). Statistics analysis was based on 4 technical repeats on pooled samples (n = 2). c Cortex of PIWIL1-knockout mice showed lower level of MAP2 immunofluorescence signal (red arrows indicate MAP2 signal in WT brain). Scale bar, 20 μm. d, e Co-electroporation of MAP2B with PIWIL1 siRNA largely attenuated the migration defect in mouse brains. Scramble vs RNAi 2; RNAi 2 + CAG vs RNAi 2 + MAP2B. Scale bar, 150 μm. Error bar, SEM, *P < 0.05, **P < 0.01, ***P < 0.001 (Student’s t-test)

Mentions: The regulation of MAPs by PIWIL1 in vivo was further validated using PIWIL1-knockout mice. As shown in Fig. 5a-c, in cortical tissues of adult PIWIL1-knockout mice, MAP2 levels were much lower than those in wild-type mice as revealed by both Western blotting (bands indicated by the arrow) and immunostaining. Mice lacking both MAP2 and MAP1B are known to exhibit fiber tract malformations and retarded neuronal migration in the brain [22]. To test whether PIWIL1 regulates neuronal migration via MAPs, we co-transfected the cDNA of one MAP member, MAP2B, together with PIWIL1 siRNA into cortical progenitors using IUE in embryonic mouse brains. We found that neuronal migration was largely rescued by co-transfection with MAP2B (Fig. 5d and e).Fig. 5


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 affects neuronal migration through regulating the expression of MAPs. a, b MAP2 levels (bands indicated by the arrow) were significantly decreased in the cortical tissue of adult PIWIL1-knockout mice (tissues were all from male animals). Statistics analysis was based on 4 technical repeats on pooled samples (n = 2). c Cortex of PIWIL1-knockout mice showed lower level of MAP2 immunofluorescence signal (red arrows indicate MAP2 signal in WT brain). Scale bar, 20 μm. d, e Co-electroporation of MAP2B with PIWIL1 siRNA largely attenuated the migration defect in mouse brains. Scramble vs RNAi 2; RNAi 2 + CAG vs RNAi 2 + MAP2B. Scale bar, 150 μm. Error bar, SEM, *P < 0.05, **P < 0.01, ***P < 0.001 (Student’s t-test)
© Copyright Policy - open-access
Related In: Results  -  Collection

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Fig5: PIWIL1 affects neuronal migration through regulating the expression of MAPs. a, b MAP2 levels (bands indicated by the arrow) were significantly decreased in the cortical tissue of adult PIWIL1-knockout mice (tissues were all from male animals). Statistics analysis was based on 4 technical repeats on pooled samples (n = 2). c Cortex of PIWIL1-knockout mice showed lower level of MAP2 immunofluorescence signal (red arrows indicate MAP2 signal in WT brain). Scale bar, 20 μm. d, e Co-electroporation of MAP2B with PIWIL1 siRNA largely attenuated the migration defect in mouse brains. Scramble vs RNAi 2; RNAi 2 + CAG vs RNAi 2 + MAP2B. Scale bar, 150 μm. Error bar, SEM, *P < 0.05, **P < 0.01, ***P < 0.001 (Student’s t-test)
Mentions: The regulation of MAPs by PIWIL1 in vivo was further validated using PIWIL1-knockout mice. As shown in Fig. 5a-c, in cortical tissues of adult PIWIL1-knockout mice, MAP2 levels were much lower than those in wild-type mice as revealed by both Western blotting (bands indicated by the arrow) and immunostaining. Mice lacking both MAP2 and MAP1B are known to exhibit fiber tract malformations and retarded neuronal migration in the brain [22]. To test whether PIWIL1 regulates neuronal migration via MAPs, we co-transfected the cDNA of one MAP member, MAP2B, together with PIWIL1 siRNA into cortical progenitors using IUE in embryonic mouse brains. We found that neuronal migration was largely rescued by co-transfection with MAP2B (Fig. 5d and e).Fig. 5

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