Ying Hung Lin

Gene-based screening for Y chromosome deletions in Taiwanese men presenting with spermatogenic failure

OBJECTIVEnTo develop a simple and rapid protocol for detecting deletions of the Y chromosome and to evaluate the feasibility of gene-based screening in men with spermatogenic failure.nnnDESIGNnProspective case study.nnnSETTINGnUniversity-based reproductive clinics and genetics laboratory.nnnPATIENT(S)nTwo hundred two infertile men presenting with severe oligozoospermia and nonobstructive azoospermia.nnnINTERVENTION(S)nFifteen gene-specific primers were used to detect deletions of Y chromosome genes in men with spermatogenic failure. A multiplex polymerase chain reaction amplification system was developed to facilitate rapid screening. Another 24 markers for sequence-tagged sites (STS) were used to ensure the adequacy of gene-based screening.nnnMAIN OUTCOME MEASURE(S)nDetection of deletions of Y chromosome genes.nnnRESULT(S)nOf 180 patients evaluated, 19 (10.6%) had deletions of one or more genes, including DFFRY, DBY, RBM1, DAZ, CDY1, and BPY2. A second round of STS-based screenings did not show an increase in the deletion rate but more clearly defined the extent of deletion in 14 of the 19 patients. In most patients, deletions detected by gene-based screening were similar to those detected by STS markers.nnnCONCLUSION(S)nGene-based screening with multiplex polymerase chain reaction is a rational alternative for detecting deletions of Y chromosome genes in infertile men.

Identification and characterization of a novel Rab GTPase-activating protein in spermatids

We have previously identified novel testis-specific genes by microarray analysis of human testicular tissues. One of the novel genes is Male Germ Cells Rab GTPase- Activating Proteins (MgcRabGAP), which is characterized by the conserved RabGAP catalytic domain, TBC (Tre2/Bub2/Cdc16). RabGAPs are involved in various physiological processes (e.g. vesicular trafficking, cytoskeletal remodelling, cell migration, etc.) by inactivating Rab proteins. In this study, we found that MgcRabGAP transcripts are mainly expressed in the mouse and human testes. The MgcRabGAP protein is expressed in the elongating and elongated spermatids. Immunofluorescence assay of mouse germ cells showed that the protein expression is enriched at the edge of the acrosomal region, neck and annulus during spermiogenesis. This MgcRabGAP is co-localized with its candidate substrate Rab3A at the acrosome/acroplaxome and neck regions of spermatids. Meanwhile, MgcRabGAP is co-localized and interacts with β-actin. In humans, the expression of MgcRabGAP is enriched at the stage of elongating spermatids. The amount of MGCRABGAP transcript is reduced in the testicular tissues of men with various types of spermatogenic defects. Considering that MGCRABGAP is exclusively expressed in post-meiotic male germ cells, the decreased transcript amount may be a phenomenon secondary to loss of germ cells in the testicular samples. Our finding strongly suggests that MgcRabGAP is involved in acrosome/acroplaxome formation and cytoskeletal reorganization via Rab activity during mammalian spermiogenesis.