chr19-46756813-G-A

Variant names:

• chr19-46756813-G-A
• rs747785577
• NM_024301.5:c.1363G>A

Variant summary

Our verdict is Likely pathogenic. The variant received 8 ACMG points: 8P and 0B. PM1 PM2 PM5 PP2 PP5

The NM_024301.5(FKRP):​c.1363G>A​(p.Ala455Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000691 in 1,447,538 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A455V) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: FKRP NM_024301.5 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:1
• Conservation: PhyloP100: 7.88
• 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: Likely_pathogenic. The variant received 8 ACMG points.

• PM1: In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 11 uncertain in NM_024301.5
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr19-46756814-C-A is described in ClinVar as [Pathogenic]. Clinvar id is 4226.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• 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.
• PP5: Variant 19-46756813-G-A is Pathogenic according to our data. Variant chr19-46756813-G-A is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 501628.We mark this variant Likely_pathogenic, oryginal submission is: [Conflicting_classifications_of_pathogenicity].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
FKRP	NM_024301.5	c.1363G>A	p.Ala455Thr	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.1363G>A	p.Ala455Thr	missense_variant	Exon 4 of 4	1	NM_024301.5	ENSP00000326570.4
FKRP	ENST00000391909.7	c.1363G>A	p.Ala455Thr	missense_variant	Exon 4 of 4	2		ENSP00000375776.2
FKRP	ENST00000597339.5	n.247-5020G>A		intron_variant	Intron 3 of 3	5
FKRP	ENST00000600646.5	n.247+8148G>A		intron_variant	Intron 3 of 3	3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 6.91e-7 AC: 1 AN: 1447538 Hom.: 0 Cov.: 32 AF XY: 0.00000139 AC XY: 1 AN XY: 719168

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.00 AC: 0 AN: 33180

American (AMR) AF: 0.00 AC: 0 AN: 42632

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 25772

East Asian (EAS) AF: 0.00 AC: 0 AN: 38994

South Asian (SAS) AF: 0.00 AC: 0 AN: 84478

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 51048

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5750

European-Non Finnish (NFE) AF: 9.04e-7 AC: 1 AN: 1105784

Other (OTH) AF: 0.00 AC: 0 AN: 59900

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.000000), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 33

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Walker-Warburg congenital muscular dystrophy Pathogenic:1

Nov 29, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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.Ala455 amino acid residue in FKRP. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 14652796, 16368217, 18671187, 23420653, 23894383). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. 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 tolerated. ClinVar contains an entry for this variant (Variation ID: 501628). This variant has not been reported in the literature in individuals affected with FKRP-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces alanine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 455 of the FKRP protein (p.Ala455Thr). -

not provided Uncertain:1

Apr 28, 2017

Eurofins Ntd Llc (ga)

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.46
BayesDel_addAF	Pathogenic	0.17	D
BayesDel_noAF	Uncertain	0.010
CADD	Uncertain	25
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.53	D;D
Eigen	Uncertain	0.24
Eigen_PC	Uncertain	0.38
FATHMM_MKL	Uncertain	0.93	D
LIST_S2	Benign	0.81	.;T
M_CAP	Pathogenic	0.33	D
MetaRNN	Uncertain	0.58	D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Benign	2.0	M;M
PhyloP100		7.9
PrimateAI	Uncertain	0.59	T
PROVEAN	Benign	-1.8	N;N
REVEL	Uncertain	0.60
Sift	Benign	0.10	T;T
Sift4G	Benign	0.25	T;T
Polyphen		0.40	B;B
Vest4		0.33
MutPred		0.50		Gain of relative solvent accessibility (P = 0.0483);Gain of relative solvent accessibility (P = 0.0483);
MVP		0.99
MPC		0.73
ClinPred		0.89	D
GERP RS		5.4
Varity_R		0.32
gMVP		0.63
Mutation Taster		=39/61	disease causing

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: rs747785577; hg19: chr19-47260070;