rs121909266

chr3-122257091-C-T

Variant summary

Our verdict is Pathogenic. Variant got 16 ACMG points: 16P and 0B. PM1 PM2 PM5 PP2 PP3 PP5_Very_Strong

The NM_000388.4(CASR):c.196C>T(p.Arg66Cys) variant causes a missense change. The variant allele was found at a frequency of 0.00000274 in 1,461,734 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R66H) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000027 (0 hom.)
• Consequence: CASR NM_000388.4 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 4.83

Genes affected

CASR (HGNC:1514): (calcium sensing receptor) The protein encoded by this gene is a plasma membrane G protein-coupled receptor that senses small changes in circulating calcium concentration. The encoded protein couples this information to intracellular signaling pathways that modify parathyroid hormone secretion or renal cation handling, and thus this protein plays an essential role in maintaining mineral ion homeostasis. Mutations in this gene are a cause of familial hypocalciuric hypercalcemia, neonatal severe hyperparathyroidism, and autosomal dominant hypocalcemia. [provided by RefSeq, Aug 2017]

ACMG classification

Verdict is Pathogenic. Variant got 16 ACMG points.

• PM1: In a hotspot region, there are 4 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 12 uncertain in NM_000388.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr3-122257092-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 650821.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP2: Missense variant where missense usually causes diseases, CASR
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.835
• PP5: Variant 3-122257091-C-T is Pathogenic according to our data. Variant chr3-122257091-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 8335.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr3-122257091-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
CASR	NM_000388.4	c.196C>T	p.Arg66Cys	missense_variant	3/7	ENST00000639785.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
CASR	ENST00000639785.2	c.196C>T	p.Arg66Cys	missense_variant	3/7	1	NM_000388.4	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000274 AC: 4 AN: 1461734 Hom.: 0 Cov.: 32 AF XY: 0.00000275 AC XY: 2 AN XY: 727192

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000116

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000270

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Familial hypocalciuric hypercalcemia 1 Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

OMIM

May 01, 1995

- -

Autosomal dominant hypocalcemia 1;C1809471:Familial hypocalciuric hypercalcemia Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Invitae

Oct 05, 2021

In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. This variant disrupts the p.Arg66 amino acid residue in CASR. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 16740594, 25104082). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. Experimental studies have shown that this missense change affects CASR function (PMID: 8702647, 16740594, 17284438, 21239511). Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive. ClinVar contains an entry for this variant (Variation ID: 8335). This variant is also known as p.Arg67Cys. This missense change has been observed in individual(s) with CASR-related conditions (PMID: 7726161, 16740594). It has also been observed to segregate with disease in related individuals. This variant is not present in population databases (ExAC no frequency). This sequence change replaces arginine with cysteine at codon 66 of the CASR protein (p.Arg66Cys). The arginine residue is highly conserved and there is a large physicochemical difference between arginine and cysteine. -

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Jun 07, 2017

The R66C variant in the CASR gene has been reported previously in the homozygous state in a newborn diagnosed with neonatal severe hyperparathyroidism (NSHPT), which prior to a parathyroidectomy had elevated concentrations of serum calcium and PTH (Pidasheva et al., 2006). This variant has also been reported in the heterozygous state in an individual with with familial hypocalciuric hypercalcemia (Chou et al., 1995). An in vitro transfection study demonstrated the R66C variant impairs cell signaling response to extracellular increases in CASR agonists in HEK293 cells (Pidasheva et al., 2006). The R66C variant is not observed in large population cohorts (Lek et al., 2016; 1000 Genomes Consortium et al., 2015; Exome Variant Server). The R66C variant is a non-conservative amino acid substitution, which is likely to impact secondary protein structure as these residues differ in polarity, charge, size and/or other properties. This substitution occurs at a position that is conserved across species. Additionally, a missense variant at the same residue (R66H) has been reported as homozygous in two siblings with NSHPT (Pidasheva et al., 2006). We interpret R66C as a likely pathogenic variant. -

Familial hypocalciuric hypercalcemia Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Oct 10, 2023

Variant summary: CASR c.196C>T (p.Arg66Cys) results in a non-conservative amino acid change in the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 251326 control chromosomes (gnomAD). c.196C>T has been reported in the literature in the heterozygous state in five related individuals with Familial Hypocalciuric Hypercalcemia (FHH) and in the homozygous state in one additional family member with Neonatal Severe Hyperparathyroidism (NSHPT) who had elevated calcium and parathyroid hormone levels and subsequently underwent a parathyroidectomy (e.g. Pollak_1994, Chou_1995). These data indicate that the variant is very likely to be associated with disease. At least two publications report experimental evidence evaluating an impact on protein function in vitro (e.g. Pidasheva_2006, Huang_2007). The variant showed reduced cell surface expression compared to the wild type protein, lacked mature glycosylation and was deficient in cell signalling responses to extracellular CASR ligands, exhibiting a response approximately 10-30% that of wild type CASR. Additionally, another variant affecting the same amino acid (p.R66H) was found to severely impact protein function and has been observed in multiple affected individuals in a family with FHH/NSHPT (Pidasheva_2006), further supporting that R66 is important for CASR function. The following publications have been ascertained in the context of this evaluation (PMID: 7726161, 17284438, 16740594, 8132750). Two submitters have cited clinical-significance assessments for this variant to ClinVar after 2014 and both classified the variant as likely pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.98
BayesDel_addAF	Pathogenic	0.40	D
BayesDel_noAF	Pathogenic	0.34
Cadd	Pathogenic	33
Dann	Pathogenic	1.0
DEOGEN2	Pathogenic	0.89	D;D;.;.
Eigen	Pathogenic	0.73
Eigen_PC	Uncertain	0.64
FATHMM_MKL	Uncertain	0.96	D
M_CAP	Uncertain	0.27	D
MetaRNN	Pathogenic	0.84	D;D;D;D
MetaSVM	Pathogenic	0.82	D
MutationAssessor	Pathogenic	3.6	H;H;H;.
MutationTaster	Benign	1.0	A;A;A
PrimateAI	Pathogenic	0.84	D
Polyphen		1.0	D;D;.;.
Vest4		0.93, 0.93
MutPred		0.65		Loss of MoRF binding (P = 0.0068);Loss of MoRF binding (P = 0.0068);Loss of MoRF binding (P = 0.0068);Loss of MoRF binding (P = 0.0068);
MVP		0.95
MPC		1.8
ClinPred		1.0	D
GERP RS		5.8
Varity_R		0.84
gMVP		0.93

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.15		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs121909266; hg19: chr3-121975938; COSMIC: COSV99949282;