Huntingtin-associated protein 1 interacts with Ahi1 to regulate cerebellar and brainstem development in mice
Guoqing Sheng, Xingshun Xu, Yung-Feng Lin, Chuan-En Wang, Juan Rong, Dongmei Cheng, Junmin Peng, Xiaoyan Jiang, Shi-Hua Li, Xiao-Jiang Li
Guoqing Sheng, Xingshun Xu, Yung-Feng Lin, Chuan-En Wang, Juan Rong, Dongmei Cheng, Junmin Peng, Xiaoyan Jiang, Shi-Hua Li, Xiao-Jiang Li
View: Text | PDF
Research Article Development

Huntingtin-associated protein 1 interacts with Ahi1 to regulate cerebellar and brainstem development in mice

Abstract

Joubert syndrome is an autosomal recessive disorder characterized by congenital malformation of the cerebellum and brainstem, with abnormal decussation in the brain. Mutations in the Abelson helper integration site 1 gene, which encodes the protein AHI1, have been shown to cause Joubert syndrome. In this study, we found that mouse Ahi1 formed a stable complex with huntingtin-associated protein 1 (Hap1), which is critical for neonatal development and involved in intracellular trafficking. Hap1-knockout mice showed significantly reduced Ahi1 levels, defective cerebellar development, and abnormal axonal decussation. Suppression of Ahi1 also decreased the level of Hap1; and truncated Ahi1, which corresponds to the mutations in Joubert syndrome, inhibited neurite outgrowth in neuronal culture. Reducing Hap1 expression suppressed the level and internalization of TrkB, a neurotrophic factor receptor that mediates neurogenesis and neuronal differentiation, which led to decreased TrkB signaling. These findings provide insight into the pathogenesis of Joubert syndrome and demonstrate the critical role of the Ahi1-Hap1 complex in early brain development.

Authors

Guoqing Sheng, Xingshun Xu, Yung-Feng Lin, Chuan-En Wang, Juan Rong, Dongmei Cheng, Junmin Peng, Xiaoyan Jiang, Shi-Hua Li, Xiao-Jiang Li

×

Figure 1

Identification of Ahi1 as a Hap1-interacting protein in the mouse brain.

Options: View larger image (or click on image) Download as PowerPoint
Identification of Ahi1 as a Hap1-interacting protein in the mouse brain....
(A) Coomassie staining of Hap1 immunoprecipitates from the brain tissues of WT and Hap1-KO mouse pups. Arrow indicates the band that is present with Hap1A and Hap1B in WT mouse brain tissue. Mass spectrometry peptide analysis identified this band as Ahi1. (B) Western blots of Hap1 immunoprecipitation confirm the coprecipitation of Ahi1 (arrow) with both Hap1A and Hap1B from WT mouse brain tissues. (C) Double immunofluorescence staining of mouse brainstem showing the colocalization of Hap1 and Ahi1 in the cytoplasmic puncta (left panels). Single labeling of the brain section with anti-Hap1 did not show bleeding of the fluorescent signal (right panels). (D) GST and GST-Hap1B were generated, and the intact form of GST-Hap1B is indicated by an arrowhead (left panel). Lysates of HEK293 cells transfected with Ahi1 were pulled down by GST-Hap1 fusion protein. Note that full-length (arrow), but not truncated, Ahi1 bound to Hap1. (E) Cotransfection of Hap1A and Ahi1 in HEK293 cells resulted in the colocalization of both proteins in cytoplasmic puncta. Scale bars: 5 μm.