Expression Profile of Mouse Gm20594, Nuclear-Encoded Humanin-Like Gene

Abstract

Background: Mitochondrial-derived peptides (MDPs) such as MOTS-c and humanin have been studied for their cytoprotective functions. In mice, humanin-encoding Mtrnr2 is a mitochondrial pseudogene, and the humanin-like peptide is encoded by the nuclear Gm20594 gene. However, endogenous tissue-specific expression profiles of Gm20594 have not yet been identified.

Methods: Mtrnr1 and Gm20594 expression was profiled via reverse transcription using only oligo(dT) primers from tissues of C57BL6/J mice. To analyze altered expression upon mitochondrial biogenesis, C2C12 myocytes and brown adipocytes were differentiated. Mitochondrial DNA copy numbers were quantified for normalization.

Results: Both Mtrnr1 and Gm20594 were highly expressed in brown adipose tissue. When normalized against mitochondrial content, Mtrnr1 was identified as being highly expressed in the duodenum, followed by the jejunum. In models of mitochondrial biogenesis, both Mtrnr1 and Gm20594 were upregulated during myocyte and brown adipocyte differentiation. Increased Mtrnr1 expression during brown adipocyte differentiation remained significant after normalization against mitochondrial DNA copy number, whereas myocyte differentiation exhibited biphasic upregulation and downregulation in early and late phases, respectively.

Conclusion: Nuclear-encoded Gm20594 showed similar expression patterns of mitochondrial-encoded Mtrnr1. Brown adipose tissue presented the highest basal expression levels of Gm20594 and Mtrnr1. When normalized against mitochondrial DNA copy number, gut tissues exhibited the highest expression of Mtrnr1. Upregulation of Mtrnr1 during mitochondrial biogenesis is independent of mitochondrial content.

Keywords: Gene expression; Gm20594; Mitochondria; Mitochondrial-derived peptide; Mtrnr1.

Fig. 1

Comparisons of cDNA detection levels according to primers of reverse transcription. Expressions of Mtrnr1 (a), Gm20594 (b), and Nd6 (c) of AML12 cells. ***p < 0.001 vs. oligo(dT).

Fig. 2

Tissue-expressional profiles of mouse MDPs. Relative expression of Mtrnr1 (a) and Gm20594 (b) in tissues of C57BL/6 mice with oligo(dT)-only reverse transcription. (c) Relative mitochondrial DNA copy number. (d) Relative expression of Mtrnr1 normalized against relative mitochondrial DNA copy number.

Fig. 3

MDP expressions in myocyte differentiation. (a) Relative expressions of myocyte differentiation markers from differentiation day 0 to 8. (b) Relative expression of Mtrnr1 and Gm20594. (c) Relative mitochondrial DNA copy numbers. (d) Relative expression of Mtrnr1 normalized against relative mitochondrial DNA copy numbers. **p < 0.01; ***p < 0.001 vs. D0.

Fig. 4

MDP expressions in brown adipocyte differentiation. (a) Relative expressions of brown adipocyte differentiation markers from differentiation day 0 and 8. (b) Relative expression of Mtrnr1 and Gm20594. (c) Relative mitochondrial DNA copy numbers. (d) Relative expression of Mtrnr1 normalized against relative mitochondrial DNA copy numbers. **p < 0.01; ***p < 0.001 vs. D0.