Telomerase Reverse Transcriptase Promoter Mutations in Bladder Cancer: High Frequency Across Stages, Detection in Urine, and Lack of Association with Outcome

Background: Hotspot mutations in the promoter of the gene coding for telomerase reverse transcriptase (TERT) have been described and proposed to activate gene expression. Objectives: To investigate TERT mutation frequency, spectrum, association with expression and clinical outcome, and potential for detection of recurrences in urine in patients with urothelial bladder cancer (UBC). Design, setting, and participants: A set of 111 UBCs of different stages was used to assess TERT promoter mutations by Sanger sequencing and TERT messenger RNA (mRNA) expression by reverse transcription-quantitative polymerase chain reaction. The two most frequent mutations were investigated, using a SNaPshot assay, in an independent set of 184 non-muscle-invasive and 173 muscle-invasive UBC (median follow-up: 53 mo and 21 mo, respectively). Voided urine from patients with suspicion of incident UBC (n = 174), or under surveillance after diagnosis of non-muscle-invasive UBC (n = 194), was tested using a SNaPshot assay. Outcome measurements and statistical analysis: Association of mutation status with age, sex, tobacco, stage, grade, fibroblast growth factor receptor 3 (FGFR3) mutation, progression-free survival, disease-specific survival, and overall survival. Results and limitations: In the two series, 78 of 111 (70%) and 283 of 357 (79%) tumors harbored TERT mutations, C228T being the most frequent substitution (83% for both series). TERT mutations were not associated with clinical or pathologic parameters, but were more frequent among FGFR3 mutant tumors (p = 0.0002). There was no association between TERT mutations and mRNA expression (p = 0.3). Mutations were not associated with clinical outcome. In urine, TERT mutations had 90% specificity in subjects with hematuria but no bladder tumor, and 73% in recurrence-free UBC patients. The sensitivity was 62% in incident and 42% in recurrent UBC. A limitation of the study is its retrospective nature. Conclusions: Somatic TERT promoter mutations are an early, highly prevalent genetic event in UBC and are not associated with TERT mRNA levels or disease outcomes. A SNaPshot assay in urine may help to detect UBC recurrences. (C) 2013 European Association of Urology. Published by Elsevier B. V. All rights reserved

Heterogeneous clinical phenotypes and cerebral malformations reflected by rotatin cellular dynamics

Recessive mutations in RTTN, encoding the protein rotatin, were originally identified as cause of polymicrogyria, a cortical malformation. With time, a wide variety of other brain malformations has been ascribed to RTTN mutations, including primary microcephaly. Rotatin is a centrosomal protein possibly involved in centriolar elongation and ciliogenesis. However, the function of rotatin in brain development is largely unknown and the molecular disease mechanism underlying cortical malformations has not yet been elucidated. We performed both clinical and cell biological studies, aimed at clarifying rotatin function and pathogenesis. Review of the 23 published and five unpublished clinical cases and genomic mutations, including the effect of novel deep intronic pathogenic mutations on RTTN transcripts, allowed us to extrapolate the core phenotype, consisting of intellectual disability, short stature, microcephaly, lissencephaly, periventricular heterotopia, polymicrogyria and other malformations. We show that the severity of the phenotype is related to residual function of the protein, not only the level of mRNA expression. Skin fibroblasts from eight affected individuals were studied by high resolution immunomicroscopy and flow cytometry, in parallel with in vitro expression of RTTN in HEK293T cells. We demonstrate that rotatin regulates different phases of the cell cycle and is mislocalized in affected individuals. Mutant cells showed consistent and severe mitotic failure with centrosome amplification and multipolar spindle formation, leading to aneuploidy and apoptosis, which could relate to depletion of neuronal progenitors often observed in microcephaly. We confirmed the role of rotatin in functional and structural maintenance of primary cilia and determined that the protein localized not only to the basal body, but also to the axoneme, proving the functional interconnectivity between ciliogenesis and cell cycle progression. Proteomics analysis of both native and exogenous rotatin uncovered that rotatin interacts with the neuronal (non-muscle) myosin heavy chain subunits, motors of nucleokinesis during neuronal migration, and in human induced pluripotent stem cell-derived bipolar mature neurons rotatin localizes at the centrosome in the leading edge. This illustrates the role of rotatin in neuronal migration. These different functions of rotatin explain why RTTN mutations can lead to heterogeneous cerebral malformations, both related to proliferation and migration defects