Insufficiency of Mrpl40 disrupts testicular structure and semen parameters in a murine model

Abstract

Approximately 31% of patients with 22q11.2 deletion syndrome (22q11.2DS) have genitourinary system disorders and 6% of them have undescended testes. Haploinsufficiency of genes on chromosome 22q11.2 might contribute to the risk of 22q11.2DS. In this study, we used mice with single-allele deletion in mitochondrial ribosomal protein L40 ( Mrpl40 +/- ) as models to investigate the function of Mrpl40 in testes and spermatozoa development. The penetrance of cryptorchidism in Mrpl40 +/- mice was found to be higher than that in wild-type (WT) counterparts. Although the weight of testes was not significantly different between the WT and Mrpl40 +/- mice, the structure of seminiferous tubules and mitochondrial morphology was altered in the Mrpl40 +/- mice. Moreover, the concentration and motility of spermatozoa were significantly decreased in the Mrpl40 +/- mice. In addition, data-independent acquisition mass spectrometry indicated that the expression of genes associated with male infertility was altered in Mrpl40 +/- testes. Our study demonstrated the important role of Mrpl40 in testicular structure and spermatozoa motility and count. These findings suggest that Mrpl40 is potentially a novel therapeutic target for cryptorchidism and decreased motility and count of spermatozoa.

Figure 1

Identification of genotypes and phenotypes of the Mrpl40^+/− mouse model. (a) The strategy used to establish the Mrpl40^+/− mouse model. (b) The genotype of the mice. The 390-bp band in Lanes 1 and 4 indicated Mrpl40^+/−, and Lanes 2 and 3 without the 390-bp band indicated WT. The 325-bp band was the positive control. M: DL2000 DNA marker. (c) Bilateral and unilateral cryptorchidism investigated in the WT and Mrpl40^+/− mice. The testes are outlined in yellow. (d) The IHC results of Mrpl40 in the testes. Scale bar = 50 μm. WT: wild type; Cas9: CRISPR-associated protein 9; sgRNA: single guide RNA; IHC: immunohistochemistry; Mrpl40: mitochondrial ribosomal protein L40.

Figure 2

Morphology of the testes. (a) The testes that were localized correctly in Mrpl40^+/− mice appeared with normal morphology. (b) The Mrpl40^+/− testes had a normal organ/body weight ratio. (c) The morphology of mitochondria in the WT and Mrpl40^+/− testes. NS: not significant. The data were analyzed by Student’s t-test and were expressed as the mean ± s.e.m. WT: wild type; Mrpl40: mitochondrial ribosomal protein L40; s.e.m.: standard error of the mean.

Figure 3

HE staining results of the testes in (a) WT and (b) Mrpl40^+/− mice. Asterisks indicate abnormal seminiferous tubules. Scale bars = 200 μm. HE: hematoxylin and eosin; WT: wild type; Mrpl40: mitochondrial ribosomal protein L40.

Figure 4

Analysis of the spermatozoa. (a) The morphology of the spermatozoa from WT and Mrpl40^+/− mice was normal. Scale bars=10 μm. (b) The sperm concentration and (c) the percent of motile spermatozoa in the Mrpl40^+/− mice was decreased. ^*P < 0.05. The data were analyzed by Student’s t-test and were expressed as the mean ± s.e.m. WT: wild type; Mrpl40: mitochondrial ribosomal protein L40; s.e.m.: standard error of the mean.