Circadian rhythm disorders are common characteristics of neurodegenerative diseases. The pathological aggregation of transactive response DNA-binding protein 43 (TDP-43) is associated with multiple neurodegenerative diseases, such as amyotrophic lateral sclerosis. However, the relationship between TDP-43 and circadian rhythm remains unknown. Here, we found that TDP-43 is rhythmically expressed both in vivo and in vitro. TDP-43 knockdown affected the expression of circadian genes, including BMAL1, CLOCK, CRY1, and PER2, and impaired autonomous circadian wheel behavior, cognitive functions, and balance abilities in mice. Furthermore, TDP-43 knockdown induced aberrant splicing of ubiquitin-specific peptidase 13 (USP13) and blocked USP13 rhythmic expression, enhancing the ubiquitination of BMAL1. Meanwhile, TDP-43 knockdown altered the rhythmic expression of phospho-AMPKα (Thr172) and platelet-type phosphofructokinase (PFKP), which may change cellular glucose uptake and ATP production. Our findings further the understanding of the role of TDP-43 dysfunction in circadian rhythm disruption in neurodegenerative diseases and provide new mechanistic evidence supporting the interaction between circadian rhythm disruption and neurodegeneration.

Background: Neurofibrillary tangle aggregated from anomalous hyperphosphorylated tau is a hallmark of Alzheimer’s disease (AD). Trans-active response DNA-binding protein of 43 kDa (TDP-43) enhances the instability and exon (E) 10 inclusion of tau mRNA. Cytoplasmic inclusion of hyperphosphorylated TDP-43 in the neurons constitutes the third most prevalent proteinopathy of AD. Casein kinase 1δ (CK1δ) is elevated in AD brain and phosphorylates TDP-43 in vitro. Objective: To determine the roles of CK1δ in phosphorylation, aggregation, and function of TDP-43 in the processing of tau mRNA. Methods: The interaction and colocalization of TDP-43 and CK1δ were analyzed by co-immunoprecipitation and immunofluorescence staining. TDP-43 phosphorylation by CK1δ was determined in vitro and in cultured cells. RIPA-insoluble TDP-43 aggregates obtained by ultracentrifugation were analyzed by immunoblots. The instability and E10 splicing of tau mRNA were studied by using a reporter of green fluorescence protein tailed with 3’-untranslational region of tau mRNA and a mini-tau gene and analyzed by real-time quantitative PCR and reverse transcriptional PCR. Results: We found that CK1δ interacted and co-localized with TDP-43. TDP-43 was phosphorylated by CK1δ at Ser379, Ser403/404, and Ser409/410 in vitro and in cultured cells, which was mutually enhanced. CK1δ overexpression promoted the aggregation of TDP-43 and suppressed its activity in enhancing the instability and E10 inclusion of tau mRNA. Conclusion: CK1δ phosphorylates TDP-43, promotes its aggregation, and inhibits its activity in promoting the instability of tau mRNA and inclusion of tau E10. Elevated CK1δ in AD brain may contribute to TDP-43 and tau pathologies directly or indirectly.

Mutations in the neuroblastoma amplified sequence ( NBAS ) gene correlate with infantile acute liver failure (ALF). Herein, we identified a novel NBAS mutation in a female infant diagnosed with recurrent ALF. Whole-exome and Sanger sequencing revealed that the proband carried a compound heterozygous mutation (c.938_939delGC and c.1342 T > C in NBAS ). NBAS c.938_939delGC was presumed to encode a truncated protein without normal function, whereas NBAS c.1342 T > C encoded NBAS harboring the conserved Cys448 residue mutated to Arg448 (p.C448R). The proportion of CD4 + T cells decreased in the patient’s peripheral CD45 + cells, whereas that of CD8 + T cells increased. Moreover, upon transfecting the same amount of DNA expression vector (ectopic expression) encoding wild-type NBAS and p.C448R NBAS, the group transfected with the p.C448R NBAS-expressing vector expressed less NBAS mRNA and protein. Furthermore, ectopic expression of the same amount of p.C448R NBAS protein as the wild-type resulted in more intracellular reactive oxygen species and the induction of apoptosis and expression of marker proteins correlating with endoplasmic reticulum stress in more cultured cells. This study indicated that p.C448R NBAS has a function different from that of wild-type NBAS and that the p.C448R NBAS mutation potentially affects T-cell function and correlates with ALF.

Abstract The mutations in neuroblastoma amplified sequence (NBAS) gene correlate with two clinical spectra: short stature with optic nerve atrophy and Pelger-Huët anomaly (SOPH) syndrome and infantile liver failure syndrome 2 (ILFS2). Here, we describe a study of a 26-month-old Chinese girl who was diagnosed with fever-triggered recurrent acute liver failure (ALF). The clinical characteristics were great elevation of liver enzymes, severe coagulopathy, and acute renal failure. Whole-exome and Sanger sequencing of the patient and his parents revealed that she carried novel compound heterozygous missense mutations in NBAS c.938_939delGC and c.1342T > C (p.Cys448Arg). The frameshift mutation c.[938_939delGC] should cause truncated NBAS protein without normal function and c.1342T > C (p.Cys448Arg) mutation affects evolutionarily conserved amino acid residues. And we found the ratio of peripheral CD3+CD4+CD45+ to CD3+CD8+CD45+ was lower in patient than that in normal children, and c.1342T > C mutation reduced expression of NBAS mRNA and protein, enriched intracellular reactive oxygen species, and induced cell apoptosis and endoplasmic reticulum stress in vitro cell models. Our study would enrich our understanding of the mechanism of NBAS mutation in regulating the ALF progress. We recommend NBAS gene analysis in children with unexplained fever-triggered recurrent ALF or liver dysfunction.

Abstract Mutations localized in the neuroblastoma amplified sequence (NBAS) gene correlate with infantile liver failure syndrome 2. In this study, we identified a novel NBAS mutation in a 26-month-old Chinese female diagnosed with fever-triggered recurrent acute liver failure (ALF). The proband exhibited highly elevated liver enzymes, severe coagulopathy, and acute renal failure. Whole-exome and Sanger sequencing revealed that the proband carried a compound heterozygous missense mutation in NBAS c.938_939delGC and c.1342T > C (p.Cys448Arg), the former of which causes a truncated NBAS protein without normal function and the latter of which affects evolutionarily conserved amino acid residues. The ratio of peripheral CD3+, CD4+, and CD45 + to CD3+, CD8+, and CD45 + cells was lower in the patient than in children without ALF. Moreover, the c.1342T > C mutation reduced the expression of NBAS mRNA and protein, enriched intracellular reactive oxygen species, and induced cell apoptosis and endoplasmic reticulum stress in in vitro cell models. Our study clarifies the mechanism by which NBAS mutations regulate ALF progression. Furthermore, we suggest employing NBAS gene detection in children with unexplained fever-triggered recurrent ALF or liver dysfunction.

The G-protein-coupled receptor 126 (GPR126) may play an important role in tumor development, although its role remains poorly understood. We found that GPR126 had higher expression in most colorectal cancer cell lines than in normal colon epithelial cell lines, and higher expression levels in colorectal cancer tissues than in normal adjacent colon tissues. GPR126 knockdown induced by shRNA inhibited cell viability and colony formation in HT-29, HCT116, and LoVo cells, decreased BrdU incorporation into newly synthesized proliferating HT-29 cells, led to an arrest of cell cycle progression at the G1 phase in HCT-116 and HT-29 cells, and suppressed tumorigenesis of HT-29, HCT116, and LoVo cells in nude mouse xenograft models. GPR126 knockdown engendered decreased transcription and translation of histone deacetylase 2 (HDAC2), previously implicated in the activation of GLI1 and GLI2 in the Hedgehog signaling pathway. Ectopic expression of HDAC2 in GPR126-silenced cells restored cell viability and proliferation, GLI2 luciferase reporter activity, partially recovered GLI2 expression, and reduced the cell cycle arrest. HDAC2 regulated GLI2 expression and, along with GLI2, it bound to the PTCH1 promoter, as evidenced by a chip assay with HT-29 cells. Purmorphamine, a hedgehog agonist, largely restored the cell viability and expression of GLI2 proteins in GPR126-silenced HT-29 cells, whereas GANT61, a hedgehog inhibitor, further enhanced the GPR126 knockdown-induced inhibitory effects. Our findings demonstrate that GPR126 regulates colorectal cancer cell proliferation by mediating the expression of HDAC2 and GLI2, therefore it may represent a suitable therapeutic target for colorectal cancer treatment.