19-46755685-G-C

Variant names:

• chr19-46755685-G-C
• rs104894683
• NM_024301.5:c.235G>C

Variant summary

Our verdict is Uncertain significance. The variant received 1 ACMG points: 3P and 2B. PM2 PP2 BP4_Moderate

The NM_024301.5(FKRP):​c.235G>C​(p.Val79Leu) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. V79M) has been classified as Benign.

• Frequency: Genomes: not found (cov: 33)
• Consequence: FKRP NM_024301.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 1.83
• Publications: 0 publications found

Genes affected

FKRP (HGNC:17997): (fukutin related protein) This gene encodes a protein which is targeted to the medial Golgi apparatus and is necessary for posttranslational modification of dystroglycan. Mutations in this gene have been associated with congenital muscular dystrophy, cognitive disability, and cerebellar cysts. Several alternatively spliced transcript variants of this gene have been described, but the full-length nature of some of these variants has not been determined. [provided by RefSeq, Oct 2008]

FKRP Gene-Disease associations (from GenCC):

• autosomal recessive limb-girdle muscular dystrophy type 2I

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Laboratory for Molecular Medicine, Orphanet, Labcorp Genetics (formerly Invitae), Ambry Genetics
• muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A5

  Inheritance: AR Classification: DEFINITIVE, STRONG, MODERATE Submitted by: Genomics England PanelApp, G2P, Ambry Genetics
• muscular dystrophy-dystroglycanopathy type B5

  Inheritance: AR Classification: DEFINITIVE, STRONG Submitted by: Myriad Women’s Health, Labcorp Genetics (formerly Invitae)
• myopathy caused by variation in FKRP

  Inheritance: AR Classification: DEFINITIVE Submitted by: ClinGen
• congenital muscular dystrophy with cerebellar involvement

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• congenital muscular dystrophy with intellectual disability

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• congenital muscular dystrophy without intellectual disability

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• muscle-eye-brain disease

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• muscular dystrophy-dystroglycanopathy, type A

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Uncertain_significance. The variant received 1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 46 curated pathogenic missense variants (we use a threshold of 10). The gene has 2 curated benign missense variants. Gene score misZ: 1.8498 (below the threshold of 3.09). Trascript score misZ: -2.4986 (below the threshold of 3.09). GenCC associations: The gene is linked to autosomal recessive limb-girdle muscular dystrophy type 2I, muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A5, congenital muscular dystrophy with intellectual disability, muscular dystrophy-dystroglycanopathy, type A, muscle-eye-brain disease, congenital muscular dystrophy with cerebellar involvement, myopathy caused by variation in FKRP, muscular dystrophy-dystroglycanopathy type B5, congenital muscular dystrophy without intellectual disability.
• BP4: Computational evidence support a benign effect (MetaRNN=0.21148461).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
FKRP	NM_024301.5	c.235G>C	p.Val79Leu	missense_variant	Exon 4 of 4	ENST00000318584.10	NP_077277.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
FKRP	ENST00000318584.10	c.235G>C	p.Val79Leu	missense_variant	Exon 4 of 4	1	NM_024301.5	ENSP00000326570.4

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 33

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Walker-Warburg congenital muscular dystrophy Uncertain:1

Aug 23, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces valine, which is neutral and non-polar, with leucine, which is neutral and non-polar, at codon 79 of the FKRP protein (p.Val79Leu). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with FKRP-related conditions. ClinVar contains an entry for this variant (Variation ID: 1475218). Algorithms developed to predict the effect of missense changes on protein structure and function output the following: SIFT: "Tolerated"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0". The leucine amino acid residue is found in multiple mammalian species, which suggests that this missense change does not adversely affect protein function. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.22
BayesDel_addAF	Uncertain	0.065	T
BayesDel_noAF	Benign	-0.14
CADD	Benign	17
DANN	Benign	0.81
DEOGEN2	Uncertain	0.45	.;T;.;T;.;.;.;.;.;T
Eigen	Benign	-0.83
Eigen_PC	Benign	-0.69
FATHMM_MKL	Uncertain	0.82	D
LIST_S2	Benign	0.64	T;.;T;T;T;T;T;T;T;T
M_CAP	Uncertain	0.28	D
MetaRNN	Benign	0.21	T;T;T;T;T;T;T;T;T;T
MetaSVM	Pathogenic	0.98	D
MutationAssessor	Benign	1.1	.;L;.;L;.;.;.;.;.;.
PhyloP100		1.8
PrimateAI	Uncertain	0.64	T
PROVEAN	Benign	-1.1	.;N;.;N;.;.;.;.;.;.
REVEL	Uncertain	0.37
Sift	Benign	0.12	.;T;.;T;.;.;.;.;.;.
Sift4G	Benign	0.29	T;T;T;T;T;T;T;T;T;T
Polyphen		0.030	.;B;.;B;.;.;.;.;.;.
Vest4		0.32, 0.32
MutPred		0.46		Loss of sheet (P = 0.1501);Loss of sheet (P = 0.1501);Loss of sheet (P = 0.1501);Loss of sheet (P = 0.1501);Loss of sheet (P = 0.1501);Loss of sheet (P = 0.1501);Loss of sheet (P = 0.1501);Loss of sheet (P = 0.1501);Loss of sheet (P = 0.1501);Loss of sheet (P = 0.1501);
MVP		0.54
MPC		0.65
ClinPred		0.12	T
GERP RS		2.6
Varity_R		0.16
gMVP		0.62
Mutation Taster		=88/12	polymorphism

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		Details are displayed if max score is > 0.2

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

Other links and lift over

dbSNP: rs104894683; hg19: chr19-47258942;