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BackgroundHigh myopia (HM) is a leading cause of blindness that has a strong genetic predisposition. However, its genetic and pathogenic mechanisms remain largely unknown. Thus, this study aims to determine the genetic profile of individuals from two large Chinese families with HM and 200 patients with familial/sporadic HM. We also explored the pathogenic mechanism of HM using HEK293 cells and a mouse model.MethodsThe participants underwent genome-wide linkage analysis and exome sequencing. Visual acuity, electroretinogram response, refractive error, optical parameters and retinal rod cell genesis were measured in knockout mice. Immunofluorescent staining, biotin-labelled membrane protein isolation and electrophysiological characterisation were conducted in cells transfected with overexpression plasmids.ResultsA novel HM locus on Xp22.2-p11.4 was identified. Variant c.539C>T (p.Pro180Leu) inGLRA2gene was co-segregated with HM in the two families. Another variant, c.458G>A (p.Arg153Gln), was identified in a sporadic sample. TheGlra2knockout mice showed myopia-related phenotypes, decreased electroretinogram responses and impaired retinal rod cell genesis. Variants c.458G>A and c.539C>T altered the localisation of GlyRα2 on the cell membrane and decreased agonist sensitivity.ConclusionGLRA2was identified as a novel HM-causing gene. Its variants would cause HM through altered visual experience by impairing photoperception and visual transmission.

Significance In addition to responding to directional cues, axons join one another as they extend to form highly organized projections. We show here that growth cones communicate with each other, and this communication is mediated by planar cell polarity signaling components, which are known to mediate cell–cell interactions in tissue polarization. This interaction is, in part, mediated by an intercellular interaction between Frizzled3 and Vangl2. Leucine-rich repeat kinase 2 (LRRK2), encoded by a Parkinson’s disease gene, regulates Frizzled3 phosphorylation and the intercellular interaction between Frizzled3 and Vangl2. Both loss-of-function and gain-of-function LRRK2 mutants show axon guidance defects, including those of the dopaminergic neurons, suggesting that this Parkinson’s disease gene plays important roles in growth cone–growth cone interactions during axon development., Axon–axon interactions are essential for axon guidance during nervous system wiring. However, it is unknown whether and how the growth cones communicate with each other while sensing and responding to guidance cues. We found that the Parkinson’s disease gene, leucine-rich repeat kinase 2 (LRRK2), has an unexpected role in growth cone–growth cone communication. The LRRK2 protein acts as a scaffold and induces Frizzled3 hyperphosphorylation indirectly by recruiting other kinases and also directly phosphorylates Frizzled3 on threonine 598 (T598). In LRRK1 or LRRK2 single knockout, LRRK1/2 double knockout, and LRRK2 G2019S knockin, the postcrossing spinal cord commissural axons are disorganized and showed anterior–posterior guidance errors after midline crossing. Growth cones from either LRRK2 knockout or G2019S knockin mice showed altered interactions, suggesting impaired communication. Intercellular interaction between Frizzled3 and Vangl2 is essential for planar cell polarity signaling. We show here that this interaction is regulated by phosphorylation of Frizzled3 at T598 and can be regulated by LRRK2 in a kinase activity-dependent way. In the LRRK1/2 double knockout or LRRK2 G2019S knockin, the dopaminergic axon bundle in the midbrain was significantly widened and appeared disorganized, showing aberrant posterior-directed growth. Our findings demonstrate that LRRK2 regulates growth cone–growth cone communication in axon guidance and that both loss-of-function mutation and a gain-of-function mutation (G2019S) cause axon guidance defects in development.

To determine the genetic etiology of deafness in a family (HN-SD01) with autosomal dominant nonsyndromic hearing loss (NSHL). Stepwise genetic analysis was performed on family HN-SD01, including hotspot variant screening, exome sequencing, virtual hearing loss gene panel, and genome-wide linkage analysis. Targeted region sequencing was used to screen ABCC1 in additional cases. Cochlear expression of Abcc1 was evaluated by messenger RNA (mRNA) and protein levels. Computational prediction, immunofluorescence, real-time quantitative polymerase chain reaction, and flow cytometry were conducted to uncover functional consequences of candidate variants. Stepwise genetic analysis identified a heterozygous missense variant, ABCC1:c.1769A>G (p.Asn590Ser), cosegregating with phenotype in HN-SD01. Screening of ABCC1 in an additional 217 cases identified candidate pathogenic variants c.692G>A (p.Gly231Asp) in a sporadic case and c.887A>T (p.Glu296Val) in a familial proband. Abcc1 expressed in stria vascularis and auditory nerve of mouse cochlea. Immunofluorescence showed p.Asn590Ser distributed in cytomembrane and cytoplasm, while wild type was shown only in cytomembrane. Besides, it generated unstable mRNA and decreased efflux capacity of ABCC1. Stepwise genetic analysis is efficient to analyze the genetic etiology of NSHL. Variants in ABCC1 are linked with NSHL and suggest an important role of extruding pumps in maintaining cochlea function.

Dynamic change of mitochondrial morphology and distribution along neuronal branches are essential for neural circuitry formation and synaptic efficacy. However, the underlying mechanism remains elusive. We show here that Pink1 knockout (KO) mice display defective dendritic spine maturation, reduced axonal synaptic vesicles, abnormal synaptic connection, and attenuated long-term synaptic potentiation (LTP). Drp1 activation via S616 phosphorylation rescues deficits of spine maturation in Pink1 KO neurons. Notably, mice harboring a knockin (KI) phosphor-null Drp1

Amyloid beta oligomers cause glutamatergic synapse degeneration by targeting the planar cell polarity components in the synapses., The signaling pathway directly controlling the maintenance of adult glutamatergic synapses has not been well understood. Planar cell polarity (PCP) signaling components were recently shown to play essential roles in the formation of glutamatergic synapses. Here, we show that they are localized in the adult synapses and are essential for their maintenance. Synapse loss at early stages of Alzheimer’s disease is thought to be induced by β-amyloid (Aβ) pathology. We found that oligomeric Aβ binds to Celsr3 and assists Vangl2 in disassembling synapses. Moreover, a Wnt receptor and regulator of PCP signaling, Ryk, is also required for Aβ-induced synapse loss. In the 5XFAD mouse model of Alzheimer’s disease, Ryk conditional knockout or a function-blocking monoclonal Ryk antibody protected synapses and preserved cognitive function. We propose that tipping of the fine balance of Wnt/PCP signaling components in glutamatergic synapses may cause synapse degeneration in neurodegenerative disorders with Aβ pathology.

Mutations in ATP13A2 cause Kufor-Rakeb syndrome, an atypical form of Parkinson’s disease. Wang et al. characterize the phenotypes of ATP13A2-deficient animals and cells and show that ATP13A2 recruits HDAC6 to lysosomes to deacetylate cortactin, modulating autophagosome–lysosome fusion and autophagy., Mutations in ATP13A2 cause Kufor-Rakeb syndrome, an autosomal recessive form of juvenile-onset atypical Parkinson’s disease (PD). Recent work tied ATP13A2 to autophagy and other cellular features of neurodegeneration, but how ATP13A2 governs numerous cellular functions in PD pathogenesis is not understood. In this study, the ATP13A2-deficient mouse developed into aging-dependent phenotypes resembling those of autophagy impairment. ATP13A2 deficiency impaired autophagosome–lysosome fusion in cultured cells and in in vitro reconstitution assays. In ATP13A2-deficient cells or Drosophila melanogaster or mouse tissues, lysosomal localization and activity of HDAC6 were reduced, with increased acetylation of tubulin and cortactin. Wild-type HDAC6, but not a deacetylase-inactive mutant, restored autophagosome–lysosome fusion, antagonized cortactin hyperacetylation, and promoted lysosomal localization of cortactin in ATP13A2-deficient cells. Mechanistically, ATP13A2 facilitated recruitment of HDAC6 and cortactin to lysosomes. Cortactin overexpression in cultured cells reversed ATP13A2 deficiency–associated impairment of autophagosome–lysosome fusion. PD-causing ATP13A2 mutants failed to rescue autophagosome–lysosome fusion or to promote degradation of protein aggregates and damaged mitochondria. These results suggest that ATP13A2 recruits HDAC6 to lysosomes to deacetylate cortactin and promotes autophagosome–lysosome fusion and autophagy. This study identifies ATP13A2 as an essential molecular component for normal autophagy flux in vivo and implies potential treatments targeting HDAC6-mediated autophagy for PD.

Synapse loss is an early event in Alzheimer’s disease and is thought to be associated with amyloid pathology and caused by Amyloid β (Aβ) oligomers. Whether and how Aβ oligomers directly target signaling pathways for glutamatergic synapse maintenance is unknown. Glutamatergic synapse development is controlled by the opposing functions of Celsr3 and Vangl2, core components of the Wnt/planar cell polarity (PCP) signaling pathway, functioning directly in the synapses. Celsr3 promotes synapse formation, whereas Vangl2 inhibits synapse formation. Here we show that oligomeric Aβ binds to Celsr3 and assists Vangl2 in disassembling synapses by disrupting the intercellular Celsr3/Frizzled3-Celsr3 complex, essential for PCP signaling. Together with Vangl2, a Wnt receptor, Ryk, is also required for Aβ oligomer-induced synapse loss in a mouse model of Alzheimer’s disease, 5XFAD, where conditional Ryk knockout protected synapses and preserved cognitive function. Our study reveals a fine balance of Wnt/PCP signaling components in glutamatergic synapse maintenance and suggests that overproduced Aβ oligomers may lead to excessive synapse loss by tipping this balance. Together with previous reports that an inhibitor of Wnt/Ryk signaling, WIF1, is found reduced in Alzheimer’s disease patients, our results suggest that the imbalance of PCP signaling in these patients may contribute to synapse loss in Alzheimer’s disease and manipulating Wnt/PCP signaling may preserve synapses and cognitive function.

The overall statistics for variants of exome sequencing for the affected subject II:3. (DOCX 12 kb)

Candidate variations after filtering. (DOCX 12 kb)

Filtering statistics for the SNVs and InDels called from the exome sequencing data. (DOCX 12 kb)

Mutations in PINK1 (PTEN-induced putative kinase 1) cause early onset familial Parkinson's disease (PD). PINK1 accumulates on the outer membrane of damaged mitochondria followed by recruiting parkin to promote mitophagy. Here, we demonstrate that BCL2/adenovirus E1B 19-kDa interacting protein 3 (BNIP3), a mitochondrial BH3-only protein, interacts with PINK1 to promote the accumulation of full-length PINK1 on the outer membrane of mitochondria, which facilitates parkin recruitment and PINK1/parkin-mediated mitophagy. Inactivation of BNIP3 in mammalian cells promotes PINK1 proteolytic processing and suppresses PINK1/parkin-mediated mitophagy. Hypoxia-induced BNIP3 expression results in increased expression of full-length PINK1 and mitophagy. Consistently, expression of BNIP3 in Drosophila suppresses muscle degeneration and the mitochondrial abnormality caused by PINK1 inactivation. Together, the results suggest that BNIP3 plays a vital role in regulating PINK1 mitochondrial outer membrane localization, the proteolytic process of PINK1 and PINK1/parkin-mediated mitophagy under physiological conditions. Functional up-regulation of BNIP3 may represent a novel therapeutic strategy to suppress the progression of PD.

Background Nance-Horan Syndrome (NHS) (OMIM: 302350) is a rare X-linked developmental disorder characterized by bilateral congenital cataracts, with occasional dental anomalies, characteristic dysmorphic features, brachymetacarpia and mental retardation. Carrier females exhibit similar manifestations that are less severe than in affected males. Methods Here, we report a four-generation Chinese family with multiple affected individuals presenting Nance-Horan Syndrome. Whole-exome sequencing combined with RT-PCR and Sanger sequencing was used to search for a genetic cause underlying the disease phenotype. Results Whole-exome sequencing identified in all affected individuals of the family a novel donor splicing site mutation (NM_198270: c.1045 + 2T > A) in intron 4 of the gene NHS, which maps to chromosome Xp22.13. The identified mutation results in an RNA processing defect causing a 416-nucleotide addition to exon 4 of the mRNA transcript, likely producing a truncated NHS protein. Conclusions The donor splicing site mutation NM_198270: c.1045 + 2T > A of the NHS gene is the causative mutation in this Nance-Horan Syndrome family. This research broadens the spectrum of NHS gene mutations, contributing to our understanding of the molecular genetics of NHS. Electronic supplementary material The online version of this article (doi:10.1186/s12881-016-0360-9) contains supplementary material, which is available to authorized users.