ClinVar Genomic variation as it relates to human health

This sequence change creates a premature translational stop signal (p.Met245Valfs*2) in the SPG11 gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in SPG11 are known to be pathogenic (PMID: 19105190, 20110243, 22154821, 26556829). This variant is present in population databases (rs312262720, gnomAD 0.01%). This premature translational stop signal has been observed in individuals with autosomal recessive hereditary spastic paraplegia with thin corpus callosum, also known as ARHSP-TCC and juvenile amyotrophic lateral sclerosis (PMID: 17322883, 17717710, 18067136, 18079167, 18332254, 18835492, 19105190, 19438933, 20110243, 22175763, 22237444, 22696581, 24833714, 27071356). ClinVar contains an entry for this variant (Variation ID: 1112). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. For these reasons, this variant has been classified as Pathogenic.

The heterozygous p.Met245ValfsTer2 variant in SPG11 was identified by our study in the compound heterozygous state, along with another pathogenic variant, in two siblings with spastic paraplegia. The presence of this variant in combination with a reported pathogenic variant and in an individual with spastic paraplegia increases the likelihood that the p.Met245ValfsTer2 variant is pathogenic. The p.Met245ValfsTer2 variant in SPG11 has been well-reported in the literature. This variant has been reported in greater than 22 individuals from Italy, Japan, France, Tunisia, Sicily, Korea, Spain, China, and Portugal with spastic paraplegia in the homozygous and compound heterozygous state, segregated with disease in 12 affected relatives from 5 families (PMID: 17717710, 20110243, 17322883, 18079167, 22175763, 18332254, 24833714, 22696581, 22237444, 18067136, 18835492), but has been identified in 0.006133% (17/277208) of chromosomes by the Genome Aggregation Database (gnomAD, http://gnomad.broadinstitute.org; dbSNP rs312262720). Although this variant has been seen in the general population, its frequency is low enough to be consistent with a recessive carrier frequency. This variant has also been reported in ClinVar (Variation ID: 1112). This variant is predicted to cause a frameshift, which alters the protein’s amino acid sequence beginning at position 245 and leads to a premature termination codon 2 amino acids downstream. This alteration is then predicted to lead to a truncated or absent protein. Loss of function of the SPG11 gene is an established disease mechanism in autosomal recessive spastic paraplegia. In summary, the p.Met245ValfsTer2variant is pathogenic based off of our findings, multiple reports of pathogenicity in ClinVar, and the literature. ACMG/AMP Criteria applied: PM2, PVS1, PM3, PP1_Moderate (Richards 2015).

Variant summary: SPG11 c.733_734delAT (p.Met245ValfsX2) results in a premature termination codon, predicted to cause a truncation of the encoded protein or absence of the protein due to nonsense mediated decay, which are commonly known mechanisms for disease. Truncations downstream of this position are associated with Spastic Paraplegia in HGMD. The variant allele was found at a frequency of 6.8e-05 in 251452 control chromosomes (gnomAD). This frequency is not higher than expected for a pathogenic variant in SPG11 causing Hereditary Spastic Paraplegia, Type 11 (6.8e-05 vs 0.0011). c.733_734delAT has been reported in the literature in multiple individuals affected with Hereditary Spastic Paraplegia (examples: Boukhris_2009 and Stevanin_2008). These data indicate that the variant is very likely to be associated with disease. Eight submitters have provided clinical-significance assessments for this variant to ClinVar after 2014 and all classified the variant as pathogenic (n=7) and likely pathogenic (n=1). Based on the evidence outlined above, the variant was classified as pathogenic.

Frameshift variant predicted to result in protein truncation or nonsense-mediated decay in a gene for which loss-of-function is a known mechanism of disease; Not observed at a significant frequency in large population cohorts (Lek et al., 2016); This variant is associated with the following publications: (PMID: 17717710, 18332254, 20110243, 22175763, 17322883, 18067136, 27071356, 31227335, 31289639, 31969655, 29980238, 31589614)

The frameshift deletion p.M245Vfs*2 in SPG11 (NM_025137.4) has been previously reported in many individuals affected with autosomal recessive hereditary spastic paraplegia with thin corpus callosum, also known as ARHSP-TCC (Stevanin et al, 2007;Del Bo et al. 2007). This variant is predicted to cause loss of normal protein function through protein truncation caused a frameshift mutation. The frame shifted sequence continues 2 residues until a stop codon is reached. The p.M245Vfs*2 variant is a loss of function variant in the gene SPG11, which is intolerant of Loss of Function variants. For these reasons, this variant has been classified as Pathogenic.

The c.733_734delAT (p.M245Vfs*2) alteration, located in coding exon 4 of the SPG11 gene, results from a deletion of 2 nucleotides from position 733 to 734, causing a translational frameshift with a predicted alternate stop codon after 2 amino acids. This alteration is expected to result in loss of function by premature protein truncation or nonsense-mediated mRNA decay. Based on data from the Genome Aggregation Database (gnomAD), the c.733_734delAT alteration was observed in 0.006% (18/282852) of total alleles studied. In multiple individuals with spastic paraplegia with thin corpus callosum, this alteration has been detected in the homozygous state or in conjunction with a second disease-causing allele (Stevanin, 2007; Boukhris, 2008; Pensato, 2014; Dong, 2018; Wei, 2019). This alteration was also identified in a patient meeting diagnostic criteria for amyotrophic lateral sclerosis (ALS) and a brain MRI which was negative for thin corpus callosum and white matter abnormalities; this individual was also heterozygous for a nonsense variant in SPG11 (Orlacchio, 2010). Based on the available evidence, this alteration is classified as pathogenic.

This variant is classified as pathogenic because it is a frameshift variant identified in the homozygote state in a single case. ClinVar contains an entry for this variant (Variation ID: 1112), it’s classified as pathogenic. This variant is not reported in the 1000 Genomes Project but is present at a low frequency in the gnomAD database [AF = 6.49e-5]. This is a recurrent variant associated with the following publication (PMID: 17322883, 18067136, 18332254, 22175763, 22696581, 27071356, 30778698, 36524102).

The observed variant c.733_734delAT (p.M245Vfs) is not reported in The 1000 Genomes database and its minor allele frequency in ExAC database is 0.0001071. The in silico prediction for the variant is pathogenic by MutationTaster2.

Variant interpreted as Pathogenic and reported on 05-07-2018 by Invitae. GenomeConnect-Invitae Patient Insights Network assertions are reported exactly as they appear on the patient-provided report from the testing laboratory. Registry team members make no attempt to reinterpret the clinical significance of the variant. Phenotypic details are available under supporting information.