Open Access Research

Transcriptome profiling of mice testes following low dose irradiation

Kirstine C Belling1*, Masami Tanaka23, Marlene Danner Dalgaard4, John Erik Nielsen4, Henrik Bjørn Nielsen1, Søren Brunak15, Kristian Almstrup4 and Henrik Leffers4

Author Affiliations

1 Center for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark, 2800 Lyngby, Denmark

2 Department of Nutrition, Junior College Division, The University of Aizu, Aizu-Wakamatsu 965-8570 Japan

3 Department of Pharmacology, St. Marianna University School of Medicine, Kawasaki 216-8511 Japan

4 Department of Growth and Reproduction, Rigshospitalet, 2100 Copenhagen, Denmark

5 Department of Disease Systems Biology, Faculty of Health Sciences, Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Blegdamsvej 3A, 2200 Copenhagen, Denmark

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Reproductive Biology and Endocrinology 2013, 11:50  doi:10.1186/1477-7827-11-50

Published: 28 May 2013

Abstract

Background

Radiotherapy is used routinely to treat testicular cancer. Testicular cells vary in radio-sensitivity and the aim of this study was to investigate cellular and molecular changes caused by low dose irradiation of mice testis and to identify transcripts from different cell types in the adult testis.

Methods

Transcriptome profiling was performed on total RNA from testes sampled at various time points (n = 17) after 1 Gy of irradiation. Transcripts displaying large overall expression changes during the time series, but small expression changes between neighbouring time points were selected for further analysis. These transcripts were separated into clusters and their cellular origin was determined. Immunohistochemistry and in silico quantification was further used to study cellular changes post-irradiation (pi).

Results

We identified a subset of transcripts (n = 988) where changes in expression pi can be explained by changes in cellularity. We separated the transcripts into five unique clusters that we associated with spermatogonia, spermatocytes, early spermatids, late spermatids and somatic cells, respectively. Transcripts in the somatic cell cluster showed large changes in expression pi, mainly caused by changes in cellularity. Further investigations revealed that the low dose irradiation seemed to cause Leydig cell hyperplasia, which contributed to the detected expression changes in the somatic cell cluster.

Conclusions

The five clusters represent gene expression in distinct cell types of the adult testis. We observed large expression changes in the somatic cell profile, which mainly could be attributed to changes in cellularity, but hyperplasia of Leydig cells may also play a role. We speculate that the possible hyperplasia may be caused by lower testosterone production and inadequate inhibin signalling due to missing germ cells.

Keywords:
Mice; Testis; Irradiation; Gene expression; Transcriptomics; Microarray; Clustering; Leydig cell; Hyperplasia