| Summary: | Objective: We have recently performed an array-based genome-wide analysis of structural variants in a cohort of patients with non-obstructive azoospermia (NOA) and found a cryptic deletion of approximately 1Mb in 11p13, spanning the WT1 gene but not PAX6, in a Portuguese patient with clinical history of cryptorchidism during childhood?. Here we performed the molecular characterization of this novel deletion, to precisely map the breakpoints of this deletion, and evaluated the prevalence of focal WT1 genetic alterations in infertile Portuguese patients with cryptorchidism. Design: Fine molecular characterization of a heterozygous large deletion in 11p13 in one azoospermic patient (with clinical history of cryptorchidism) and screening for WT1 exonic microdeletions and mutations in a group of 31 Portuguese patients with uni- or bi-lateral cryptorchidism. Materials and Methods: Multiplex ligation-dependent probe amplification (MLPA), Long Range PCR; PCR amplification of the WT1 exons and proximal flanking sequences followed by Sanger sequencing. Results: We confirmed by MLPA the ~1Mb deletions at 11p13 spanning six genes - WT1, PRRG4, QSER1, TCP11L1, CSTF3 and HIPK3. Examination of the deletion breakpoint showed that it lies within highly homologous Alu Y sequences. Therefore the likely mechanism for this deletion was Alu-mediated non-allelic homologous recombination (NAHR). No mutations were found in the single allele present in this patient suggesting that the phenotype probably results from WT1 haploinsufficiency. We found no additional WT1 alterations in our group of patients with cryptorchidism. Conclusions: To our knowledge this is the smallest as yet described deletion encompassing the WT1 gene, which results in a non-syndromic clinical presentation of infertility. Repeat-mediated non-allelic recombination is an alternative mechanism for 11p13 deletions spanning WT1. Based on our results WT1 genetic defects are not frequently involved in isolated cryptorchidism, even though more patients should be analyzed. Support: This work was partially funded by the Portuguese Foundation for Science and Technology FCT/MCTES (PIDDAC) and co-financed by European funds (FEDER) through the COMPETE program, research grant PTDC/SAU-GMG/101229/2008 to AML. IPATIMUP is an Associate Laboratory of the Portuguese Ministry of Science, Technology, and Higher Education and is partially supported by FCT. AML is the recipient of a postdoctoral fellowship from FCT (SFRH/BPD/73366/2010).
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