Generation of Pmel-dependent conditional and inducible Cre-driver mouse line for melanocytic-targeted gene manipulation.

Conditional and inducible gene targeting using Cre/loxP-mediated recombination is a powerful reverse genetics approach used to study spatiotemporal gene functions in specified cell types. To enable temporal gene manipulation in the melanocyte lineage, we established a novel inducible Cre-driver mouse line by targeting an all-in-one tetracycline/doxycycline (Dox)-inducible Cre expression cassette into the Pmel locus (PmelP2A-TetON3G-TRE3G-iCre ), a gene locus preferentially expressed in pigment cells. By crossing these Cre-driver mice with a strong Cre-reporter mouse line, Gt(ROSA)26Sortm9(CAG-tdTomato)Hze , we show the effectiveness of the PmelP2A-TetON3G-TRE3G-iCre mouse line in facilitating Dox-inducible Cre/loxP recombination in a wide variety of pigment cell lineages including hair follicle melanocytes and their stem cells. Furthermore, to demonstrate proof of concept, we ablated Notch signaling postnatally in the PmelP2A-TetON3G-TRE3G-iCre mice. In agreement with the previously reported phenotype, induced ablation of Notch signaling in the melanocyte lineage resulted in premature hair graying, demonstrating the utility of the PmelP2A-TetON3G-TRE3G-iCre allele. Therefore, the PmelP2A-TetON3G-TRE3G-iCre mouse line is suitable for assessing gene functions in melanocytes using an in vivo inducible reverse genetics approach. Furthermore, we unexpectedly identified previously unrecognized PMEL-expressing cells in non-pigmentary organs in the mice, suggesting unanticipated functions of PMEL other than melanosome formation.

A DISC1 point mutation promotes oligomerization and impairs information processing in a mouse model of schizophrenia.

Disrupted-in-schizophrenia 1 (DISC1) is strongly associated with schizophrenia, but it remains elusive how the modification of the intermolecular interaction of DISC1 affects the information processing in brain. We show that a DISC1 point mutation alters intermolecular cohesiveness promoting the phase separation, and disrupts sensorimotor gating monitored by the prepulse inhibition in a mouse model of schizophrenia. Although the conformation of DISC1 partial peptide with the schizophrenia-related mutation L607F in human or the corresponding L604F in mouse was essentially indistinguishable from the wild type (WT) as long as monitored by fluorescence, circular dichroism, ultracentrifugation, dynamic light scattering and nuclear magnetic resonance, the atomic force microscopy was able to detect their morphological distinctions. The WT peptides were round and well dispersed, while mutants were inhomogeneous and disrupted to form dimer to trimer that aligned along one direction without apparent aggregate formation. Homozygous L604F mutant mice created by CRISPR exhibited the significant decrease in DISC1 level in the immunohistopathology at the hippocampal region compared to the WTs. The ratio of prepulse inhibition of the homozygous mutant mice was significantly impaired compared to WTs. Altered DISC1 distribution or function caused by aberrant intermolecular interactions may contribute to information processing characteristics in schizophrenia.