Imbalance between Expression of FOXC2 and Its lncRNA in Lymphedema-Distichiasis Caused by Frameshift Mutations

Abstract

Forkhead-box C2 (FOXC2) is a transcription factor involved in lymphatic system development. FOXC2 mutations cause Lymphedema-distichiasis syndrome (LD). Recently, a natural antisense was identified, called lncRNA FOXC2-AS1, which increases FOXC2 mRNA stability. No studies have evaluated FOXC2 and FOXC2-AS1 blood expression in LD and healthy subjects. Here, we show that FOXC2 and FOXC-AS1 expression levels were similar in both controls and patients, and a significantly higher amount of both RNAs was observed in females. A positive correlation between FOXC2 and FOXC2-AS1 expression was found in both controls and patients, excluding those with frameshift mutations. In these patients, the FOXC2-AS1/FOXC2 ratio was about 1:1, while it was higher in controls and patients carrying other types of mutations. The overexpression or silencing of FOXC2-AS1 determined a significant increase or reduction in FOXC2 wild-type and frameshift mutant proteins, respectively. Moreover, confocal and bioinformatic analysis revealed that these variations caused the formation of nuclear proteins aggregates also involving DNA. In conclusion, patients with frameshift mutations presented lower values of the FOXC2-AS1/FOXC2 ratio, due to a decrease in FOXC2-AS1 expression. The imbalance between FOXC2 mRNA and its lncRNA could represent a molecular mechanism to reduce the amount of FOXC2 misfolded proteins, protecting cells from damage.

The emerging roles of long noncoding RNAs in lymphatic vascular development and disease

“…In a non-cancer context, the same mechanism might regulate lymphatic valve formation and collecting lymphatic vessel specialization. Based on Zhang et al [ 208 ] and Missaglia et al [ 216 ]. eIF4F eukaryotic initiation factor 4F, m7G methyl-7-guanosine (cap), miRISC microRNA-induced silencing complex, ORF open reading frame, PABP poly(A)-binding protein …”

“…Recently experimental evidence has emerged suggesting that at least some of the above FOXC2-AS1 -mediated mechanisms are operational in non-cancer cells. Missaglia et al [ 216 ] detected endogenous expression of FOXC2-AS1 in blood cells of healthy individuals and LD patients. Furthermore, they found that, consistent with the results obtained in cancer cell lines, endogenous FOXC2-AS1 positively regulates the expression of wild-type FOXC2 and its frameshift LD mutant in normal, non-cancer cells.…”

Low Efficacy of Genetic Tests for the Diagnosis of Primary Lymphedema Prompts Novel Insights into the Underlying Molecular Pathways

“…The expression of PROX1 is regulated by SOX18 and GATA2, while the latter also controls the expression of FOXC2 [12]. FOXC2, a member of the forkheadbox (FOX) family, regulates the development of several systems during embryogenesis, particularly the lymphatic and blood vascular system [75,76].…”

“…Among them, NR2F2 is negatively regulated by NOTCH signaling through HEY2 expression [77]. Moreover, they can activate FOXC2, such as CDK5 and FOXC2-AS1 [75,78]. PROX1 and FOXC2 expression is also increased by CHD5 through the β-catenin pathway, regulating lymphatic vessels and valve development [79,80].…”