Homozygous TMEM127 mutations in 2 patients with bilateral pheochromocytomas

miRNA-23b-5p affects the proliferation, migration and invasion of osteosarcoma by targeting TMEM127

BACKGROUND

Osteosarcoma (OS) has become one of the highest mortality cancers in the world due to its late diagnosis, rapid metastasis and rapid recurrence. MicroRNAs can regulate a variety of signaling pathwas involved in cancer development, such as cell proliferation, apoptosis and migration.

OBJECTIVE

In this study, we studied the biological effects and molecular regulation of mir-23b-5p on human osteosarcoma cells.

METHODS

The proliferation of mir-23b-5p in osteosarcoma was measured by CCK8 method and EDU method. In addition, the target population was screened through the database, and the luciferase reporter gene was used to determine the association between miRNA and target gene TMEM127. We verified this result by Western blot.

RESULTS

We found that mir-23b-5p promotes the progression of osteosarcoma by regulating TMEM127.

CONCLUSIONS

The results of this study show that mir-23b-5p affects the proliferation, metastasis and invasion of OS by targeting TMEM127.

Genotype-Phenotype Features of Germline Variants of the TMEM127 Pheochromocytoma Susceptibility Gene: A 10-Year Update

PURPOSE

This work aimed to evaluate genotype-phenotype associations in individuals carrying germline variants of transmembrane protein 127 gene (TMEM127), a poorly known gene that confers susceptibility to pheochromocytoma (PHEO) and paraganglioma (PGL).

DESIGN

Data were collected from a registry of probands with TMEM127 variants, published reports, and public databases.

MAIN OUTCOME ANALYSIS

Clinical, genetic, and functional associations were determined.

RESULTS

The cohort comprised 110 index patients (111 variants) with a mean age of 45 years (range, 21-84 years). Females were predominant (76 vs 34, P < .001). Most patients had PHEO (n = 94; 85.5%), although PGL (n = 10; 9%) and renal cell carcinoma (RCC, n = 6; 5.4%) were also detected, either alone or in combination with PHEO. One-third of the cases had multiple tumors, and known family history was reported in 15.4%. Metastatic PHEO/PGL was rare (2.8%). Epinephrine alone, or combined with norepinephrine, accounted for 82% of the catecholamine profiles of PHEO/PGLs. Most variants (n = 63) occurred only once and 13 were recurrent (2-12 times). Although nontruncating variants were less frequent than truncating changes overall, they were predominant in non-PHEO clinical presentations (36% PHEO-only vs 69% other, P < .001) and clustered disproportionately within transmembrane regions (P < .01), underscoring the relevance of these domains for TMEM127 function. Integration of clinical and previous experimental data supported classification of variants into 4 groups based on mutation type, localization, and predicted disruption.

CONCLUSIONS

Patients with TMEM127 variants often resemble sporadic nonmetastatic PHEOs. PGL and RCC may also co-occur, although their causal link requires further evaluation. We propose a new classification to predict variant pathogenicity and assist with carrier surveillance.

Functional Characterization of TMEM127 Variants Reveals Novel Insights into Its Membrane Topology and Trafficking

CONTEXT

TMEM127 is a poorly known tumor suppressor gene associated with pheochromocytomas, paragangliomas, and renal carcinomas. Our incomplete understanding of TMEM127 function has limited our ability to predict variant pathogenicity.

PURPOSE

To better understand the function of the transmembrane protein TMEM127 we undertook cellular and molecular evaluation of patient-derived germline variants.

DESIGN

Subcellular localization and steady-state levels of tumor-associated, transiently expressed TMEM127 variants were compared to the wild-type protein using immunofluorescence and immunoblot analysis, respectively, in cells genetically modified to lack endogenous TMEM127. Membrane topology and endocytic mechanisms were also assessed.

RESULTS

We identified 3 subgroups of mutations and determined that 71% of the variants studied are pathogenic or likely pathogenic through loss of membrane-binding ability, stability, and/or internalization capability. Investigation into an N-terminal cluster of missense variants uncovered a previously unrecognized transmembrane domain, indicating that TMEM127 is a 4- transmembrane, not a 3-transmembrane domain-containing protein. Additionally, a C-terminal variant with predominant plasma membrane localization revealed an atypical, extended acidic, dileucine-based motif required for TMEM127 internalization through clathrin-mediated endocytosis.

CONCLUSION

We characterized the functional deficits of several germline TMEM127 variants and identified novel structure-function features of TMEM127. These findings will assist in determining pathogenicity of TMEM127 variants and will help guide future studies investigating the cellular role of TMEM127.