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1.
Nucleic Acids Res ; 52(10): 5732-5755, 2024 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-38597682

RESUMO

Expansion of a G4C2 repeat in the C9orf72 gene is associated with familial Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Dementia (FTD). To investigate the underlying mechanisms of repeat instability, which occurs both somatically and intergenerationally, we created a novel mouse model of familial ALS/FTD that harbors 96 copies of G4C2 repeats at a humanized C9orf72 locus. In mouse embryonic stem cells, we observed two modes of repeat expansion. First, we noted minor increases in repeat length per expansion event, which was dependent on a mismatch repair pathway protein Msh2. Second, we found major increases in repeat length per event when a DNA double- or single-strand break (DSB/SSB) was artificially introduced proximal to the repeats, and which was dependent on the homology-directed repair (HDR) pathway. In mice, the first mode primarily drove somatic repeat expansion. Major changes in repeat length, including expansion, were observed when SSB was introduced in one-cell embryos, or intergenerationally without DSB/SSB introduction if G4C2 repeats exceeded 400 copies, although spontaneous HDR-mediated expansion has yet to be identified. These findings provide a novel strategy to model repeat expansion in a non-human genome and offer insights into the mechanism behind C9orf72 G4C2 repeat instability.


Assuntos
Proteína C9orf72 , Expansão das Repetições de DNA , Instabilidade Genômica , Animais , Humanos , Camundongos , Esclerose Lateral Amiotrófica/genética , Proteína C9orf72/genética , Modelos Animais de Doenças , Quebras de DNA de Cadeia Dupla , Expansão das Repetições de DNA/genética , Demência Frontotemporal/genética , Técnicas de Introdução de Genes , Instabilidade Genômica/genética , Proteína 2 Homóloga a MutS/genética
2.
Stem Cell Reports ; 18(1): 394-409, 2023 01 10.
Artigo em Inglês | MEDLINE | ID: mdl-36525967

RESUMO

Rats were more frequently used than mice to model human disease before mouse embryonic stem cells (mESCs) revolutionized genetic engineering in mice. Rat ESCs (rESCs) were first reported over 10 years ago, yet they are not as frequently used as mESCs. CRISPR-based gene editing in zygotes is widely used in rats but is limited by the difficulty of inserting or replacing DNA sequences larger than about 10 kb. We report here the generation of germline-competent rESC lines from several rat strains. These rESC lines maintain their potential for germline transmission after serial targeting with bacterial artificial chromosome (BAC)-based targeting vectors, and CRISPR-Cas9 cutting can increase targeting efficiency. Using these methods, we have successfully replaced entire rat genes spanning up to 101 kb with the human ortholog.


Assuntos
Células-Tronco Embrionárias , Degeneração Retiniana , Humanos , Ratos , Animais , Camundongos , Edição de Genes , Engenharia Genética , Sistemas CRISPR-Cas/genética
3.
Sci Rep ; 12(1): 14079, 2022 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-35982097

RESUMO

Humanized liver rodent models, in which the host liver parenchyma is repopulated by human hepatocytes, have been increasingly used for drug development and disease research. Unlike the leading humanized liver mouse model in which Fumarylacetoacetate Hydrolase (Fah), Recombination Activating Gene (Rag)-2 and Interleukin-2 Receptor Gamma (Il2rg) genes were inactivated simultaneously, generation of similar recipient rats has been challenging. Here, using Velocigene and 1-cell-embryo-targeting technologies, we generated a rat model deficient in Fah, Rag1/2 and Il2rg genes, similar to humanized liver mice. These rats were efficiently engrafted with Fah-expressing hepatocytes from rat, mouse and human. Humanized liver rats expressed human albumin and complement proteins in serum and showed a normal liver zonation pattern. Further, approaches were developed for gene delivery through viral transduction of human hepatocytes either in vivo, or in vitro prior to engraftment, providing a novel platform to study liver disease and hepatocyte-targeted therapies.


Assuntos
Hepatócitos , Hepatopatias , Animais , Modelos Animais de Doenças , Hepatócitos/metabolismo , Humanos , Fígado/metabolismo , Hepatopatias/metabolismo , Camundongos , Ratos
4.
Mol Pharmacol ; 64(4): 890-904, 2003 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-14500746

RESUMO

Acute desensitization of many guanine nucleotide-binding protein-coupled receptors (GPCRs) requires receptor phosphorylation and subsequent binding of an arrestin. GPCRs are substrates for phosphorylation by several classes of kinases. Gastrin-releasing peptide receptor (GRPr) is phosphorylated by a kinase other than protein kinase C (PKC) after exposure to agonist and is also a substrate for PKC-dependent phosphorylation after treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA). Using GRPr mutants, we examined receptor domains required for agonist- and TPA-induced phosphorylation of GRPr and consequences of these phosphorylation events on GRPr signaling via Gq. Agonist- and TPA-stimulated GRPr phosphorylation in cells require an intact carboxyl terminal domain (CTD). GRPr is phosphorylated in vitro by GPCR kinase 2 (GRK2) and multiple PKC isoforms. An intact DRY motif is required for agonist-stimulated phosphorylation in cells, and agonist-dependent GRK2 phosphorylation in vitro. Although GRPr CTD mutants do not show enhanced in vitro coupling to Gq relative to intact GRPr, CTD mutants have more potent Gq-dependent signaling in cells. Acute desensitization involves CTD-independent processes because desensitization can precede ligand binding in intact GRPr and CTD mutants. TPA-mediated impairment of GRPr-Gq signaling in cells also requires an intact CTD. Similar to GRK2 phosphorylation, PKC phosphorylation reduces GRPr-Gq coupling by approximately 80% in vitro. Arrestin translocation to plasma membrane requires agonist, an intact DRY motif, and GRPr phosphorylation. Therefore, agonist- and PKC-induced GRPr phosphorylation sites are in nearby regions of the receptor, and phosphorylation at both sites has similar functional consequences for Gq signaling.


Assuntos
Proteína Quinase C/metabolismo , Receptores da Bombesina/metabolismo , Células 3T3 , Sequência de Aminoácidos , Animais , Arrestina/metabolismo , Transporte Biológico , Bombesina/metabolismo , Cálcio/metabolismo , Camundongos , Camundongos Endogâmicos BALB C , Dados de Sequência Molecular , Mutação , Fosforilação , Estrutura Terciária de Proteína , Transdução de Sinais
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