LRRK2 plays an important role in Parkinson's disease (PD), but its biological functions are largely unknown. Here, we cloned the homolog of human LRRK2, characterized its expression, and investigated its biological functions in zebrafish. The blockage of zebrafish LRRK2 (zLRRK2) protein by morpholinos caused embryonic lethality and severe developmental defects such as growth retardation and loss of neurons. In contrast, the deletion of the WD40 domain of zLRRK2 by morpholinos targeting splicing did not induce severe embryonic developmental defects; rather it caused Parkinsonism-like phenotypes, including loss of dopaminergic neurons in diencephalon and locomotion defects. These neurodegenerative and locomotion defects could be rescued by over-expressing zLRRK2 or hLRRK2 mRNA. The administration of L-dopa could also rescue the locomotion defects, but not the neurodegeneration. Taken together, our results demonstrate that zLRRK2 is an ortholog of hLRRK2 and that the deletion of WD40 domain of zLRRK2 provides a disease model for PD.

Histone deacetylases (HDACs) are key transcription regulators that function by deacetylating histones/transcription factors and modifying chromatin structure. In this work, we showed that chemical inhibition of HDACs by valproic acid (VPA) led to impaired liver development in zebrafish mainly by inhibiting specification, budding, and differentiation. Formation of exocrine pancreas but not endocrine pancreas was also inhibited. The liver defects induced by VPA correlate with suppressed total HDAC enzymatic activity, but are independent of angiogenesis inhibition. Gene knockdown by morpholino demonstrated that hdac3 is specifically required for liver formation while hdac1 is more globally required for multiple development processes in zebrafish including liver/exocrine pancreas formation. Furthermore, overexpression of hdac3 but not hdac1 partially rescued VPA induced small liver. One mechanism by which hdac3 regulates zebrafish liver growth is through inhibiting growth differentiation factor 11 (gdf11), a unique target of hdac3 and a member of the transforming growth factor beta family. Simultaneous overexpression or morpholino knockdown showed that hdac3 and gdf11 function antagonistically in zebrafish liver development. These results revealed a novel and specific role of hdac3 in liver development and the distinct functions between hdac1 and hdac3 in zebrafish embryonic development.

BackgroundAs a genetic disorder of abnormal pigmentation, the molecular basis of dyschromatosis universalis hereditaria (DUH) had remained unclear until recently when ABCB6 was reported as a causative gene of DUH.MethodologyWe performed genome-wide linkage scan using Illumina Human 660W-Quad BeadChip and exome sequencing analyses using Agilent SureSelect Human All Exon Kits in a multiplex Chinese DUH family to identify the pathogenic mutations and verified the candidate mutations using Sanger sequencing. Quantitative RT-PCR and Immunohistochemistry was performed to verify the expression of the pathogenic gene, Zebrafish was also used to confirm the functional role of ABCB6 in melanocytes and pigmentation.ResultsGenome-wide linkage (assuming autosomal dominant inheritance mode) and exome sequencing analyses identified ABCB6 as the disease candidate gene by discovering a coding mutation (c.1358C>T; p.Ala453Val) that co-segregates with the disease phenotype. Further mutation analysis of ABCB6 in four other DUH families and two sporadic cases by Sanger sequencing confirmed the mutation (c.1358C>T; p.Ala453Val) and discovered a second, co-segregating coding mutation (c.964A>C; p.Ser322Lys) in one of the four families. Both mutations were heterozygous in DUH patients and not present in the 1000 Genome Project and dbSNP database as well as 1,516 unrelated Chinese healthy controls. Expression analysis in human skin and mutagenesis interrogation in zebrafish confirmed the functional role of ABCB6 in melanocytes and pigmentation. Given the involvement of ABCB6 mutations in coloboma, we performed ophthalmological examination of the DUH carriers of ABCB6 mutations and found ocular abnormalities in them.ConclusionOur study has advanced our understanding of DUH pathogenesis and revealed the shared pathological mechanism between pigmentary DUH and ocular coloboma.