CAPN3 c.1746-20C>G variant is hypomorphic for LGMD R1 calpain 3-related

Magdalena Mroczek, Inna Inashkina, Janis Stavusis, Pawel Zayakin, Andrey Khrunin, Ieva Micule, Victorija Kenina, Anna Zdanovica, Jana Zídková, Lenka Fajkusová, Svetlana Limborska, Anneke J. van der Kooi, Esther Brusse, Lea Leonardis, Ales Maver, Sander Pajusalu, Katrin Õunap, Sanna Puusepp, Paula Dobosz, Mateusz SypniewskiBirute Burnyte, Baiba Lace (Coresponding Author)

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


The investigated intronic CAPN3 variant NM_000070.3:c.1746-20C>G occurs in the Central and Eastern Europe with a frequency of >1% and there are conflicting interpretations on its pathogenicity. We collected data on 14 patients carrying the CAPN3 c.1746-20C>G variant in trans position with another CAPN3 pathogenic/likely pathogenic variant. The patients compound heterozygous for the CAPN3 c.1746-20C>G variant presented a phenotype consistent with calpainopathy of mild/medium severity. This variant is most frequent in the North/West regions of Russia and may originate from that area. Molecular studies revealed that different splicing isoforms are produced in the muscle. We hypothesize that c.1746-20C>G is a hypomorphic variant with a reduction of RNA and protein expression and only individuals having a higher ratio of abnormal isoforms are affected. Reclassification of the CAPN3 variant c.1746-20C>G from variant with a conflicting interpretation of pathogenicity to hypomorphic variant explains many unidentified cases of limb girdle muscular dystrophy R1 calpain 3-related in Eastern and Central Europe.

Original languageEnglish
Pages (from-to)1347-1353
Number of pages7
JournalHuman Mutation
Issue number10
Publication statusPublished - Oct 2022


  • calpainopathy
  • CAPN3
  • hypomorphic variant
  • LGMD
  • LGMD R1 calpain 3-related

Field of Science*

  • 3.1 Basic medicine

Publication Type*

  • 1.1. Scientific article indexed in Web of Science and/or Scopus database


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