ABSTRACT
4.5SH RNA is a highly abundant, small rodent-specific noncoding RNA that localizes to nuclear speckles enriched in pre-mRNA-splicing regulators. To investigate the physiological functions of 4.5SH RNA, we have created mutant mice that lack the expression of 4.5SH RNA. The mutant mice exhibited embryonic lethality, suggesting that 4.5SH RNA is an essential species-specific noncoding RNA in mice. RNA-sequencing analyses revealed that 4.5SH RNA protects the transcriptome from abnormal exonizations of the antisense insertions of the retrotransposon SINE B1 (asB1), which would otherwise introduce deleterious premature stop codons or frameshift mutations. Mechanistically, 4.5SH RNA base pairs with complementary asB1-containing exons via the target recognition region and recruits effector proteins including Hnrnpm via its 5' stem loop region. The modular organization of 4.5SH RNA allows us to engineer a programmable splicing regulator to induce the skipping of target exons of interest. Our results also suggest the general existence of splicing regulatory noncoding RNAs.
Subject(s)
RNA Splicing , RNA, Small Untranslated , Mice , Animals , RNA Splicing/genetics , Exons/genetics , Retroelements/genetics , Codon, Nonsense , Alternative SplicingABSTRACT
BACKGROUND: Most testicular tumors are germ cell tumors; sex cord stromal tumors are infrequent, accounting for only 3-5% of testicular tumors. Unclassified sex cord stromal tumors are extremely rare. Generally, 10% of sex cord stromal tumors are malignant. We report a case of malignant unclassified sex cord stromal tumor with retroperitoneal lymph node metastasis at first visit and a corresponding literature review. CASE PRESENTATION: A 72-year-old Japanese man visited our department primarily for indolent right scrotum enlargement in September 2020. Blood biochemistry examination, urinalysis, and tumor markers (alpha-fetoprotein, human chorionic gonadotropin, and lactate dehydrogenase) showed no abnormal findings. Contrast-enhanced computed tomography showed enlarged para-aortic lymph node (18 × 16 and 10 × 102 mm); a 50 × 452 mm mass with uneven contents was found in the right testicle. The patient underwent inguinal orchiectomy in September 2020. As per immunohistochemistry, the tumor cells were diffusely positive for SF-1 and Ki-67, partially positive for inhibin, and negative for CAM5.2, CK7, CK20, C-KIT, CD30, LCA, GATA-3, TTF-1, and PAX8. Calretinin was expressed in approximately 5% of tumor cells; thus, sex cord/gonadal stroma components were considered to be involved. The final pathological diagnosis was unclassified malignant sex cord stromal tumor. The patient was diagnosed with pT1, N1, M0, S0, and tumor-node-metastasis stage IIA disease. The patient received postoperative chemotherapy with four courses of etoposide and cisplatin therapy from November 2020. Post-chemotherapeutic computed tomography showed new metastatic lesions including lung, liver, pancreas, and para-aortic lymphadenopathy, which increased in size. Disease progression was observed. Cancer genome research was performed using the OncoGuide National Cancer Center oncopanel system; however, no gene mutation for which the drug could be expected to be effective was found. The patient opted for best supportive care at a nearby hospital and died from cancer progression in January 2022. CONCLUSION: We encountered a case of malignant testicular unclassified sex cord stromal tumor pathologically diagnosed as testicular tumor with retroperitoneal lymph node metastasis in a patient who underwent inguinal orchiectomy. Future data collection is necessary to establish multimodality therapy for malignant testicular unclassified sex cord stromal tumor.
