Altered gene dosage confirms the genetic interaction between FIAT and αNAC

Abstract

Factor inhibiting ATF4-mediated transcription (FIAT) interacts with Nascent polypeptide associated complex And coregulator alpha (αNAC). In cultured osteoblastic cells, this interaction contributes to maximal FIAT-mediated inhibition of Osteocalcin (Ocn) gene transcription. We set out to demonstrate the physiological relevance of this interaction by altering gene dosage in compound Fiat and Naca (encoding αNAC) heterozygous mice. Compound Naca+/−; Fiat+/− heterozygous animals were viable, developed normally, and exhibited no significant difference in body weight compared with control littermate genotypes. Animals with a single Fiat allele had reduced Fiat mRNA expression without changes in the expression of related family members. Expression of the osteocyte differentiation marker Dmp1 was elevated in compound heterozygotes. Static histomorphometry parameters were assessed at 8 weeks of age using microcomputed tomography (μCT). Trabecular measurements were not different between genotypes. Cortical thickness and area were not affected by gene dosage, but we measured a significant increase in cortical porosity in compound heterozygous mice, without changes in biomechanical parameters. The bone phenotype of compound Naca+/−; Fiat+/− heterozygotes confirms that FIAT and αNAC are part of a common genetic pathway and support a role for the FIAT/αNAC interaction in normal bone physiology.

NACA and LRP6 Are Part of a Common Genetic Pathway Necessary for Full Anabolic Response to Intermittent PTH

“…However, gene dosage manipulation of Naca did not affect its expression (data not shown). This was also observed in other models of compound heterozygosity involving Naca [27], suggesting that the control of the expression of Naca is not copy-number-dependent. However, every gene dosage manipulation involving Naca that we performed highlighted its genetic interaction as part of distinct signaling cascades [6,27].…”

Dephosphorylation of the transcriptional cofactor NACA by the PP1A phosphatase enhances cJUN transcriptional activity and osteoblast differentiation

“…4A), several ribosome-associated proteins interacting with NACA, including ribosomal protein L38 (RPL38). More importantly, among the previously known transcriptional partners of NACA, we observed interaction with TXLNG (FIAT) and TXLNA (47)(48)(49)(50)(51)(52). Taken together these observations are supportive of the fidelity of our purification method.…”

FIAT deletion increases bone mass but does not prevent high-fat-diet-induced metabolic complications

“…The Fiat -deficient mouse strain has been described previously ( 23 ). The McGill institutional animal care and use committee reviewed and approved all animal procedures, which followed the guidelines of the Canadian Council on Animal Care.…”

“…Water was provided ad libitum . DNA was prepared from tail snips using standard procedures and analyzed using polymerase chain reactions (PCRs) for the presence of the Fiat wild-type (WT) and targeted alleles, as previously described ( 23 ).…”