NM_014365.3:c.421A>C

Variant names:

• chr12-119187078-A-C
• rs104894351
• NM_014365.3:c.421A>C

Variant summary

Our verdict is Likely pathogenic. The variant received 8 ACMG points: 8P and 0B. PM1 PM2 PM5 PP3_Moderate

The NM_014365.3(HSPB8):​c.421A>C​(p.Lys141Gln) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic 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. K141T) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: HSPB8 NM_014365.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 8.36
• Publications: 49 publications found

Genes affected

HSPB8 (HGNC:30171): (heat shock protein family B (small) member 8) The protein encoded by this gene belongs to the superfamily of small heat-shock proteins containing a conservative alpha-crystallin domain at the C-terminal part of the molecule. The expression of this gene in induced by estrogen in estrogen receptor-positive breast cancer cells, and this protein also functions as a chaperone in association with Bag3, a stimulator of macroautophagy. Thus, this gene appears to be involved in regulation of cell proliferation, apoptosis, and carcinogenesis, and mutations in this gene have been associated with different neuromuscular diseases, including Charcot-Marie-Tooth disease. [provided by RefSeq, Jul 2008]

HSPB8 Gene-Disease associations (from GenCC):

• neuronopathy, distal hereditary motor, autosomal dominant

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• Charcot-Marie-Tooth disease axonal type 2L

  Inheritance: AD Classification: STRONG, SUPPORTIVE Submitted by: Labcorp Genetics (formerly Invitae), Orphanet
• neuronopathy, distal hereditary motor, type 2A

  Inheritance: AD Classification: STRONG Submitted by: Labcorp Genetics (formerly Invitae)
• autosomal dominant distal axonal motor neuropathy-myofibrillar myopathy syndrome

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• distal hereditary motor neuropathy type 2

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Likely_pathogenic. The variant received 8 ACMG points.

• PM1: In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 7 uncertain in NM_014365.3
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr12-119187079-A-C is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 637689.Status of the report is no_assertion_criteria_provided, 0 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.932

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HSPB8	NM_014365.3	c.421A>C	p.Lys141Gln	missense_variant	Exon 2 of 3	ENST00000281938.7	NP_055180.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
HSPB8	ENST00000281938.7	c.421A>C	p.Lys141Gln	missense_variant	Exon 2 of 3	1	NM_014365.3	ENSP00000281938.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Charcot-Marie-Tooth disease axonal type 2L Uncertain:1

Jun 28, 2019

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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. Variants that disrupt the p.Lys141 amino acid residue in HSPB8 have been observed in affected individuals (PMID: 15122253, 20538880). This suggests that it is a clinically significant residue, and that other variants that disrupt this residue are likely to be causative of disease. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C0"). This variant has not been reported in the literature in individuals with HSPB8-related disease. This variant is not present in population databases (ExAC no frequency). This sequence change replaces lysine with glutamine at codon 141 of the HSPB8 protein (p.Lys141Gln). The lysine residue is highly conserved and there is a small physicochemical difference between lysine and glutamine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.96
BayesDel_addAF	Pathogenic	0.36	D
BayesDel_noAF	Pathogenic	0.27
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.61	D
Eigen	Uncertain	0.34
Eigen_PC	Uncertain	0.46
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.93	D
M_CAP	Uncertain	0.15	D
MetaRNN	Pathogenic	0.93	D
MetaSVM	Benign	-0.88	T
MutationAssessor	Benign	1.1	L
PhyloP100		8.4
PrimateAI	Uncertain	0.73	T
PROVEAN	Benign	-1.6	N
REVEL	Pathogenic	0.83
Sift	Uncertain	0.0050	D
Sift4G	Uncertain	0.010	D
Polyphen		0.99	D
Vest4		0.90
MutPred		0.81		Loss of methylation at K141 (P = 0.0146);
MVP		0.99
MPC		0.89
ClinPred		0.92	D
GERP RS		5.7
PromoterAI		0.013	Neutral
Varity_R		0.63
gMVP		0.74
Mutation Taster		=54/46	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: rs104894351; hg19: chr12-119624883;