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Expression of Tom34 splicing isoforms in mouse testis and knockout of Tom34 in mice
Kazutoyo Terada1, Shota Ueno, Kentaro Yomogida
1Department of Molecular Genetics, Kumamoto University School of Medicine, Honjo 2-2-1, Kumamoto 860-0811, Japan. terada@gpo.kumamoto-u.ac.jp
Abstract:
The 34-kDa translocase of the outer mitochondrial membrane (Tom34) is a putative mammalian-specific factor involved in protein import into mitochondria. We analyzed the genomic sequence of the mouse Tom34 gene and found it has two alternative initial exons. Using reverse transcription and the polymerase chain reaction (RT-PCR), we found that these two mRNAs differs only in the 5'-proximal sequences corresponding to the two initial exons (exon 1a and 1b). Tom34 mRNA with exon 1a (Tom34a) is expressed ubiquitously, while that with exon 1b (Tom34b) is expressed only in mature testicular germ cells. To explore the in vivo function of Tom34 proteins, we generated Tom34-deficient mice by targeted disruption. The Tom34(-/-) mice were viable and grew normally and had a normal Mendelian inheritance pattern. Male as well as female Tom34(-/-) mice were fertile. In vitro-preprotein import into isolated mitochondria showed no apparent difference between Tom34(-/-) and wild-type mice. These results indicate that Tom34 is dispensable for mouse growth and development under optimal conditions.
Insights
The translocase of the outer mitochondrial membrane (Tom34) gene has two mRNA variants, with one specific to testicular germ cells. Tom34-deficient mice showed normal development and fertility, indicating dispensability for growth.
Area of Science:
- Mitochondrial biology
- Molecular genetics
- Mammalian development
Background:
- The translocase of the outer mitochondrial membrane (Tom34) is a mammalian-specific protein import factor.
- Mitochondrial protein import is crucial for cellular function and organismal health.
Purpose of the Study:
- To investigate the in vivo function of Tom34.
- To determine the role of alternative splicing in Tom34 mRNA expression.
- To assess the necessity of Tom34 for mouse development and fertility.
Main Methods:
- Genomic sequence analysis of the mouse Tom34 gene.
- Reverse transcription and polymerase chain reaction (RT-PCR) to analyze mRNA variants.
- Generation of Tom34-deficient mice via targeted gene disruption.
- Assessment of mouse viability, growth, Mendelian inheritance, fertility, and in vitro mitochondrial protein import.
Main Results:
- Two alternative initial exons (1a and 1b) in the mouse Tom34 gene lead to two mRNA variants (Tom34a and Tom34b).
- Tom34a mRNA is ubiquitously expressed, while Tom34b is specific to mature testicular germ cells.
- Tom34-deficient mice (Tom34(-/-)) were viable, fertile, and exhibited normal growth and Mendelian inheritance.
- No significant differences in in vitro mitochondrial preprotein import were observed between Tom34(-/-) and wild-type mice.
Conclusions:
- Tom34 exhibits alternative splicing with tissue-specific expression of one variant in germ cells.
- Tom34 is dispensable for mouse growth, development, and fertility under normal conditions.
- The precise in vivo function of Tom34 in mice remains to be elucidated, particularly under stress conditions.