Calmodulin lysine methyl transferase (CaM KMT) is ubiquitously expressed and highly conserved from plants to vertebrates. CaM is frequently trimethylated at Lys-115, however, the role of CaM methylation in vertebrates has not been studied. CaM KMT was found to be homozygously deleted in the 2P21 deletion syndrome that includes 4 genes. These patients present with cystinuria, severe intellectual disabilities, hypotonia, mitochondrial disease and facial dysmorphism. Two siblings with deletion of three of the genes included in the 2P21 deletion syndrome presented with cystinuria, hypotonia, a mild/moderate mental retardation and a respiratory chain complex IV deficiency. To be able to attribute the functional significance of the methylation of CaM in the mouse and the contribution of CaM KMT to the clinical presentation of the 2p21deletion patients, we produced a mouse model lacking only CaM KMT with deletion borders as in the human 2p21deletion syndrome. No compensatory activity for CaM methylation was found. Impairment of complexes I and IV, and less significantly III, of the mitochondrial respiratory chain was more pronounced in the brain than in muscle. CaM KMT is essential for normal body growth and somatosensory development, as well as for the proper functioning of the adult mouse brain. Developmental delay was demonstrated for somatosensory function and for complex behavior, which involved both basal motor function and motivation. The mutant mice also had deficits in motor learning, complex coordination and learning of aversive stimuli. The mouse model contributes to the evaluation of the role of methylated CaM. CaM methylation appears to have a role in growth, muscle strength, somatosensory development and brain function. The current study has clinical implications for human patients. Patients presenting slow growth and muscle weakness that could result from a mitochondrial impairment and mental retardation should be considered for sequence analysis of the CaM KMT gene.

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Published in PLOS Genetics, v. 11, no. 8, article e1005388, p. 1-22.

© 2015 Haziza et al.

This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

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Funding Information

The study was partially funded by grant number 787/05 of Israel Science Foundation to RP. The fund provided for the creation of the mouse model and its initial characterization. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

journal.pgen.1005388.s001.TIF (532 kB)
S1 Fig. Generation of the CaM KMT knockout construct.

journal.pgen.1005388.s002.TIF (570 kB)
S2 Fig. Homologous recombination in G418 resistant ES cells detected by PCR.

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S3 Fig. Validation of translation in the knock out mice.

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S4 Fig. Quantitative PCR of PRELP cDNA in quadriceps (hind limb) muscles of mice.

journal.pgen.1005388.s005.TIF (1099 kB)
S5 Fig. Measurements of cystine in the urine of two CaM KMT-/- C57Bl6J male adult (4 and 10 month old) mice in comparison to comparable CaM KMT+/+.

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S6 Fig. Fragmentation on Maldi TOF of peptides from CaM.

journal.pgen.1005388.s007.DOCX (16 kB)
S1 Table. Developmental profile test.

journal.pgen.1005388.s008.DOCX (18 kB)
S2 Table. Developmental profile statistics.

journal.pgen.1005388.s009.DOCX (15 kB)
S3 Table. Adult mice behavior.

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