ABSTRACT
The genes HMGCS2 and HMGCL encode the two main enzymes for ketone-body synthesis, mitochondrial HMG-CoA synthase and HMG-CoA lyase. Here, we identify and describe possible splice variants of these genes in human tissues. We detected an alternative transcript of HMGCS2 carrying a deletion of exon 4, and two alternative transcripts of HMGCL with deletions of exons 5 and 6, and exons 5, 6 and 7, respectively. All splice variants maintained the reading frame. However, Western blot studies and overexpression measurements in eukaryotic or prokaryotic cell models did not reveal HL or mHS protein variants. Both genes showed a similar distribution of the inactive variants in different tissues. Surprisingly, the highest percentages were found in tissues where almost no ketone bodies are synthesized: heart, skeletal muscle and brain. Our results suggest that alternative splicing might coordinately block the two main enzymes of ketogenesis in specific human tissues.
Subject(s)
Alternative Splicing/genetics , Biosynthetic Pathways/genetics , Hydroxymethylglutaryl-CoA Synthase/genetics , Ketone Bodies/biosynthesis , Mitochondria/enzymology , Mitochondria/genetics , Oxo-Acid-Lyases/genetics , Blotting, Western , Computational Biology , HEK293 Cells , Humans , Hydroxymethylglutaryl-CoA Synthase/chemistry , Hydroxymethylglutaryl-CoA Synthase/metabolism , Isoenzymes/chemistry , Isoenzymes/genetics , Isoenzymes/metabolism , Oxo-Acid-Lyases/chemistry , Oxo-Acid-Lyases/metabolism , Protein Structure, Secondary , Real-Time Polymerase Chain ReactionABSTRACT
Cornelia de Lange syndrome (CdLS) manifests facial dysmorphic features, growth and cognitive impairment, and limb malformations. Mutations in three genes (NIPBL, SMC1A, and SMC3) of the cohesin complex and its regulators have been found in affected patients. Here, we present clinical and molecular characterization of 30 unrelated patients with CdLS. Eleven patients had mutations in NIPBL (37%) and three patients had mutations in SMC1A (10%), giving an overall rate of mutations of 47%. Several patients shared the same mutation in NIPBL (p.R827GfsX2) but had variable phenotypes, indicating the influence of modifiers in CdLS. Patients with NIPBL mutations had a more severe phenotype than those with mutations in SMC1A or those without identified mutations. However, a high incidence of palate defects was noted in patients with SMC1A mutations. In addition, we observed a similar phenotype in both male and female patients with SMC1A mutations. Finally, we report the first patient with an SMC1A mutation and the Sandifer complex.
