ClinVar Genomic variation as it relates to human health

This variant was determined to be pathogenic according to ACMG Guidelines, 2015 [PMID:25741868].

Published functional studies demonstrate a damaging effect: failure to restore p16ink4A/pRB pathway signaling, increased sensitivity to ionizing radiation, and destabilization of heterochromatin-associated proteins (Filesi et al., 2005; Nitta et al., 2006; di Masi et al., 2008); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; This variant is associated with the following publications: (PMID: 23891399, 24375749, 25637381, 18604166, 12075506, 14627682, 12788894, 16046620, 19764019, 28663758, 25823658, 19084400, 17848409, 31589614, 32041611, 32376792, 34135346, 33422685, 10939567, 33038109, 15473259, 29854317, 25324471, 16809772, 10080180, 31383942)

This sequence change replaces arginine, which is basic and polar, with histidine, which is basic and polar, at codon 527 of the LMNA protein (p.Arg527His). This variant is present in population databases (rs57520892, gnomAD 0.02%). This missense change has been observed in individuals with autosomal recessive mandibuloacral dysplasia (PMID: 12075506, 14627682). It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 14499). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt LMNA protein function with a positive predictive value of 95%. Experimental studies have shown that this missense change affects LMNA function (PMID: 12075506, 18604166, 25324471, 25823658). For these reasons, this variant has been classified as Pathogenic.

The p.Arg527His variant in LMNA has been reported in the homozygous or compound heterozygous state in 10 individuals with mandiculoacral dysplasia (MAD) and segregated with disease in 5 affected individuals from 4 families (Novelli 2002, Shen 2003, Simha 2003, Garavelli 2009). It has also been identified in 6/31826 Latino chromosomes by gnomAD (http://gnomad.broadinstitute.org), however, this frequency is low enough to be consistent with a recessive carrier frequency. This variant has also been reported in ClinVar (Variation ID: 14499). In vitro functional studies support an impact on protein function (Novelli 2002, Amati 2004, Filesi 2005, Nitta 2006, Lombardi 2007, Meaburn 2007, di Masi 2008, Evangelisti 2015). Three additional variants involving this codon (p.Arg527) have been identified in individuals with MAD (Stenson 2017). In summary, this variant meets criteria to be classified as pathogenic for autosomal recessive MAD. ACMG/AMP Criteria applied: PM3_VeryStrong, PS4, PM5_Strong, PP1_Strong, PS3_Moderate, BP4.

The p.R527H variant (also known as c.1580G>A), located in coding exon 9 of the LMNA gene, results from a G to A substitution at nucleotide position 1580. The arginine at codon 527 is replaced by histidine, an amino acid with highly similar properties. This alteration has been reported in several homozygous individuals with autosomal recessive mandibuloacral dysplasia (MAD) (Shen JJ et al. J. Med. Genet., 2003 Nov;40:854-7; Garavelli L et al. Am. J. Med. Genet. A, 2009 Oct;149A:2258-64; Sakka et al. Eur J Med Genet, 2021 Feb;64:104138; Jéru I et al. Genes (Basel), 2021 Sep;12:[Epub ahead of print]). Compound heterozygosity (p.R527H/p.V440M) has also been reported in an individual with overlapping MAD and laminopathy features that were considered atypical along with a limb-girdle-like myopathy (Lombardi F et al. J. Clin. Endocrinol. Metab., 2007 Nov;92:4467-71). Heterozygous carrier family members and healthy population cohort participants have been reported to be unaffected with MAD or other laminopathy-related phenotypes (Dron JS et al. BMC Med Genomics, 2020 02;13:23; Lacaze P et al. NPJ Genom Med, 2021 Jun;6:51; Sakka et al. Eur J Med Genet, 2021 Feb;64:104138). Functional studies demonstrate that lamin A plays an important role in TGFbeta 2 regulation and that this alteration affects genomic stability and DNA damage response with the accumulation of lamin A precursor protein after X-ray exposure (Novelli G et al. Am. J. Hum. Genet., 2002 Aug;71:426-31; Evangelisti C et al. Oncotarget, 2015 Apr;6:7424-37; di Masi A et al. Cell Cycle, 2008 Jul;7:2030-7). This amino acid position is well conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Based on the supporting evidence, this variant is expected to be causative of mandibuloacral dysplasia (MAD) when present along with a second pathogenic variant on the other allele; however, its clinical significance for autosomal dominant laminopathy-related phenotypes is unclear.

This missense variant replaces arginine with histidine at codon 527 of the lamin A/C proteins. Computational prediction suggests that this variant may have deleterious impact on protein structure and function (internally defined REVEL score threshold >= 0.7, PMID: 27666373). In a transgenic mouse model, this variant has been associated with phenotypes relevant for mandibuloacral dysplasia type A syndrome while muscle phenotypes are normal (PMID: 33458588). Fibroblast cell cultures from the transgenic mice displayed nuclear envelope aberrations, accumulation of the lamin A precursor protein, proliferation, and senescence rate defects (PMID: 33458588). Another functional study has shown that cells from a homozygous carrier show abnormal nuclear morphology, while cells from a heterozygous carrier show normal nuclear morphology (PMID: 12075506). Other functional studies have suggested that this variant may increase sensitivity to ionizing radiation (PMID:18604166), affect DNA synthesis (PMID 25324471) and fail to downregulate TGFbeta-2 secretion (PMID: 25823658). This variant has been associated with autosomal recessive mandibuloacral dysplasia and Charcot-Marie-Tooth disease in several families and has been reported in the homozygous or compound heterozygous states in multiple affected individuals (PMID: 12075506, 14627682, 25286833, 32376792, 33038109, 33422685, 34680903, Xu et al. 2019 doi: 10.3969/j.issn.1000-3606.2019.09.010). Most affected carriers showed no signs of cardiac involvement except for one individual who was also affected with dilated cardiomyopathy (PMID: 33422685). Heterozygous parents were reported to be healthy. This variant has also been identified in 10/250812 chromosomes in the general population by the Genome Aggregation Database (gnomAD). Based on the available evidence, this variant is classified as a Variant of Uncertain Significance for autosomal dominant cardiomyopathy, although it is known to cause autosomal recessive mandibuloacral dysplasia and Charcot-Marie-Tooth disease (ClinVar variation ID: 14499).

This missense variant replaces arginine with histidine at codon 527 of the lamin A/C proteins. Computational prediction suggests that this variant may have deleterious impact on protein structure and function (internally defined REVEL score threshold >= 0.7, PMID: 27666373). In a transgenic mouse model, this variant has been associated with phenotypes relevant for mandibuloacral dysplasia type A syndrome while muscle phenotypes are normal (PMID: 33458588). Fibroblast cell cultures from the transgenic mice displayed nuclear envelope aberrations, accumulation of the lamin A precursor protein, proliferation, and senescence rate defects (PMID: 33458588). Another functional study has shown that cells from a homozygous carrier show abnormal nuclear morphology, while cells from a heterozygous carrier show normal nuclear morphology (PMID: 12075506). Other functional studies have suggested that this variant may increase sensitivity to ionizing radiation (PMID:18604166), affect DNA synthesis (PMID 25324471) and fail to downregulate TGFbeta-2 secretion (PMID: 25823658). This variant has been associated with autosomal recessive mandibuloacral dysplasia and Charcot-Marie-Tooth disease in several families and has been reported in the homozygous or compound heterozygous states in multiple affected individuals (PMID: 12075506, 14627682, 25286833, 32376792, 33038109, 33422685, 34680903, Xu et al. 2019 doi: 10.3969/j.issn.1000-3606.2019.09.010). Most affected carriers showed no signs of cardiac involvement except for one individual who was also affected with dilated cardiomyopathy (PMID: 33422685). Heterozygous parents were reported to be healthy. This variant has also been identified in 10/250812 chromosomes in the general population by the Genome Aggregation Database (gnomAD). Based on the available evidence, this variant is classified as a Variant of Uncertain Significance for autosomal dominant cardiomyopathy, although it is known to cause autosomal recessive mandibuloacral dysplasia and Charcot-Marie-Tooth disease (ClinVar variation ID: 14499).