Disruption of murine Tcte3-3 induces tissue specific apoptosis via co-expression of Anxa5 and Pebp1

https://doi.org/10.1016/j.compbiolchem.2014.10.005Get rights and content

Highlights

  • Tcte3 (T-complex testis expressed 3) is an accessory component of axonemal and cytoplasmic dynein which expresses predominantly in meiotic and postmeiotic germ cells.

  • 2D-gel electrophoresis, mass spectrometry and qRT–PCR analyses were performed to elucidate the differential expression of genes, in both wild-type and homozygous Tcte3-3 mice.

  • In an effort to identify the possible role of Tcte3 in sperm development, we employed a set of experimental and in-silico based approaches.

  • Our findings elucidated several co-expressed partners of Tcte3 including Anxa5 and Pebp1, whose functional coherence may help in better understanding of apoptotic induction.

  • A complete understanding of controlling factors which have implications in regulating tissue-specific Tcte3 expression would provide additional insights into the gene control events.

  • Our data would contribute to a better understanding of testes-specific transcriptional control of genes involved in apoptosis by addressing the cooperative influence of diverse regulatory partners.

Abstract

Programmed cell death or apoptosis plays a vital physiological role in the development and homeostasis. Any discrepancy in apoptosis may trigger testicular and neurodegenerative diseases, ischemic damage, autoimmune disorders and many types of cancer. Tcte3 (T-complex testis expressed 3) is an accessory component of axonemal and cytoplasmic dynein which expresses predominantly in meiotic and postmeiotic germ cells. It plays an essential role during spermatogenesis; however, to explore its diverse and complex functioning in male germ cell apoptosis, requires further prosecution. Here, 2D-gel electrophoresis, mass spectrometry and qRT–PCR analyses were performed to elucidate the differential expression of genes, in both wild-type and homozygous Tcte3-3 mice. We observed an increased expression of Tcte3 in homozygotes as compared to wild-type testes. Perpetually, an increased expression of Anxa5 and Pebp1, while a lower expression of Rsph1 was detected in Tcte3-3−/− mice. We propose that over-expression of Pebp1 and Anxa5 in Tcte3-3−/− testes might be due to increased apoptosis. To evaluate this possibility, testes specific microarray data set extracted from NCBI gene ontology omnibus (GEO) was used to cluster the possible co-expression partners of Tcte3. Further functional coherence of compiled candidate genes was monitored computationally by studying the common TFBS overlapped at the regulatory regions. Differential expression of Tcte3-3 and its involvement in apoptosis may provide a basis for the investigation of transcriptional specificities of other Tcte3 paralogs (Tcte3-1 and Tcte3-2). A complete understanding of controlling factors which have implications in regulating tissue-specific Tcte3 expression would provide additional insights into the gene control events. The collective knowledge may prove useful for the development of novel therapeutic regimen and would open new avenues in defining selective roles of Tcte3 in germ cell development.

Introduction

The coordinated balance and tight regulation among cell proliferation, differentiation and apoptosis is critical to control various biological events. The process of programmed cell death or apoptosis plays a critical physiological role in development and homeostasis (Steller, 1995, Jacobson et al., 1997). Apoptosis is considered as a vital component of various processes including spermatogenesis, neurogenesis, normal cell turnover, proper development and functioning of the immune system, hormone-dependent atrophy, embryonic development and chemical-induced cell death (Oppenheim, 1991, de Rooij and Grootegoed, 1998). Any alteration or inappropriate apoptosis (either too little or too much) may lead to the onset of a number of abnormalities including testicular diseases (de Rooij and Grootegoed, 1998), neurodegenerative diseases, ischemic damage, autoimmune disorders and many types of cancer. Although many of the key apoptotic proteins have been identified, the complete understanding of molecular mechanisms and signaling pathways that control cell cycle arrest and apoptosis need to be explored which contemplate designing therapeutic strategy to modulate the apoptotic effecter machinery (Strasser et al., 2000, Levy and Holzbaur, 2006).

Recently, it has been reported that dyneins have both direct and indirect roles in male germ cell apoptosis which results in male infertility phenotype (Rashid et al., 2010). Dynein is a large multi-subunit protein complex that powers minus end-directed movement along microtubules. It consists of two heavy chains of 530 kD (Paschal et al., 1987, Holzbaur and Vallee, 1994), that constitute the motors themselves. It also contains a number of noncatalytic subunits, conspicuously two intermediate chains of 74 kD, four light intermediate chains of 55 kD and a number of less characterized light chains such as LC8, Tctex1 or Rp3 and Tcte3 (Rappold et al., 1992, King et al., 1998, Hirokawa et al., 2010). Dyneins are classified into two functional categories: axonemal and cytoplasmic (Paschal et al., 1987, Pazour et al., 1999, Sakakibara et al., 1999). Axonemal dyneins are responsible for the movement of cilia and flagella, while cytoplasmic form of dynein serves many cellular functions, including regulation of mitotic checkpoint (Howell et al., 2001), organization of the Golgi apparatus (Vaughan, 2005), minus-end-directed transport of vesicles including endosomes and lysosomes. They also carry out retrograde axonal transport in neurons (Vallee et al., 2004) and implicate in the clearance of protein aggregates (Ravikumar et al., 2005).

Tcte3 is a component of outer dynein arm complex, initially characterized in Chlamydomonas as a homolog of LC2 (light chain 2) (Patel-King et al., 1997). Although Tcte3 is predominantly expressed in testis, its expression had also been monitored in several other tissues lacking cilia or flagella (DiBella et al., 2001, Neesen et al., 2002). Previously, we reported that at least three copies of Tcte3 exist in mouse genome and subsequent inactivation of Tcte3-3 copy results in sperm motility defects thereby resulting in partial male infertility phenotype (Rashid et al., 2010). Evidently, Tcte3-3−/− testis exhibited an increased rate of apoptosis in spermiogenesis. It is however unclear why loss of Tcte3-3 results in apoptosis of male germ cells. Here, in an effort to identify the possible role of Tcte3 in sperm development, we employed a set of experimental and in-silico based approaches. Our findings elucidated several co-expressed partners of Tcte3 including Anxa5 and Pebp1, whose functional coherence may help in better understanding of apoptotic induction.

Section snippets

Sample preparation

Tcte3-3−/− mice (Rashid et al., 2010) were obtained from Institute of Human Genetics, Goettingen, Germany and kept at the animal facility of NCB, Quaid-i-Azam University (www.qau.edu.pk). Tcte3-3 gene was originally disrupted in mixed genetic (129/SvJ/C57BL/6J) background by homologous recombination. Later on, 20 adult male mice were sacrificed by CO2 overdose as approved by the Animal Care and Use Committee of the University of Goettingen, Germany. Testicular and brain tissues were dissected

Increased amount of Tcte3 modulates the expression patterns of Rsph1, Pebp1 and Anxa5 in testis

In mouse, three Tcte3 paralogs were identified through BLAT search using ENSEMBL genome browser (www.ensembl.org) designated as Tcte3-1 [ID: ENSMUSG00000079710], Tcte3-2 [ID: ENSMUSG00000036648] and Tcte3-3 [ID: ENSMUSG00000079707], respectively. These three gene copies were localized at the minus strand of mouse chromosome 17 at 15101153–15115621, 15132803–15147148 and 15164115–15178523, respectively. Further comparison of Tcte3 transcripts through BLAST2 (www.ncbi.nlm.nih.gov) revealed minor

Discussion

Among dynein light chains including LC8 (DYNLL, Tctex1/RP3 (DYNLT) and Rbl (DYNLRB), Tcte3 has been initially characterized as a testicular protein which plays a unique role in the axonemal assembly (Pazour et al., 1999). However, subsequent expression of Tcte3 in tissues lacking cilia or flagella (DiBella et al., 2001, Neesen et al., 2002) demonstrated additional roles of this protein. Previously, we reported that Tcte3-3 mutant mice exhibit defects in spermatogenesis due to apoptosis of male

Conflict of interest

The authors declared no conflict of interest.

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