title: The High Level of Aberrant Splicing of ISCU in Slow-Twitch Muscle May Involve the Splicing Factor SRSF3.
abstract: Hereditary myopathy with lactic acidosis (HML) is an autosomal recessive disease caused by an intronic one-base mutation in the iron-sulfur cluster assembly (ISCU) gene, resulting in aberrant splicing. The incorrectly spliced transcripts contain a 100 or 86 bp intron sequence encoding a non-functional ISCU protein, which leads to defects in several Fe-S containing proteins in the respiratory chain and the TCA cycle. The symptoms in HML are restricted to skeletal muscle, and it has been proposed that this effect is due to higher levels of incorrectly spliced ISCU in skeletal muscle compared with other energy-demanding tissues. In this study, we confirm that skeletal muscle contains the highest levels of incorrect ISCU splice variants compared with heart, brain, liver and kidney using a transgenic mouse model expressing human HML mutated ISCU. We also show that incorrect splicing occurs to a significantly higher extent in the slow-twitch soleus muscle compared with the gastrocnemius and quadriceps. The splicing factor serine/arginine-rich splicing factor 3 (SRSF3) was identified as a potential candidate for the slow fiber specific regulation of ISCU splicing since this factor was expressed at higher levels in the soleus compared to the gastrocnemius and quadriceps. We identified an interaction between SRSF3 and the ISCU transcript, and by overexpressing SRSF3 in human myoblasts we observed increased levels of incorrectly spliced ISCU, while knockdown of SRSF3 resulted in decreased levels. We therefore suggest that SRSF3 may participate in the regulation of the incorrect splicing of mutant ISCU and may, at least partially, explain the muscle-specific symptoms of HML.
authors: Department of Medical Biosciences, Medical and Clinical Genetics, Umeå University, Umeå, Sweden.
authors: Denise F R
authors: http://orcid.org/0000-0001-6632-5770
authors: DF
authors: Rawcliffe
authors: Department of Medical Biosciences, Medical and Clinical Genetics, Umeå University, Umeå, Sweden.
authors: Lennart
authors: L
authors: Österman
authors: Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience, Umeå University Hospital, Umeå, Sweden.
authors: Hans
authors: H
authors: Lindsten
authors: Department of Medical Biosciences, Medical and Clinical Genetics, Umeå University, Umeå, Sweden.
authors: Monica
authors: M
authors: Holmberg
mesh_terms: D000140:Acidosis, Lactic / Q000151:congenital* / Q000235:genetics / Q000473:pathology; D000818:Animals; D002478:Cells, Cultured; D006801:Humans; D007506:Iron-Sulfur Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D018482:Muscle, Skeletal / Q000378:metabolism*; D009135:Muscular Diseases / Q000151:congenital* / Q000235:genetics / Q000473:pathology; D016297:Mutagenesis, Site-Directed; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism; D012313:RNA / Q000302:isolation & purification / Q000378:metabolism; D034622:RNA Interference; D012326:RNA Splicing; D034741:RNA, Small Interfering / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D000068103:Serine-Arginine Splicing Factors / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism
chemical_list: D007506:Iron-Sulfur Proteins; D034741:RNA, Small Interfering; C491388:SRSF3 protein, human; D000068103:Serine-Arginine Splicing Factors; D012313:RNA