15-64963728-C-T

Variant names:

• chr15-64963728-C-T
• rs2140402170
• NM_016630.7:c.819G>A

Variant summary

Our verdict is Likely benign. The variant received -1 ACMG points: 2P and 3B. PM2 BP4_Moderate BP7

The NM_016630.7(SPG21):​c.819G>A​(p.Leu273Leu) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,314 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: SPG21 NM_016630.7 synonymous
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 1.05
• Publications: 0 publications found

Genes affected

SPG21 (HGNC:20373): (SPG21 abhydrolase domain containing, maspardin) The protein encoded by this gene binds to the hydrophobic C-terminal amino acids of CD4 which are involved in repression of T cell activation. The interaction with CD4 is mediated by the noncatalytic alpha/beta hydrolase fold domain of this protein. It is thus proposed that this gene product modulates the stimulatory activity of CD4. Mutations in this gene are associated with autosomal recessive spastic paraplegia 21 (SPG21), also known as mast syndrome. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Aug 2014]

SPG21 Gene-Disease associations (from GenCC):

• mast syndrome

  Inheritance: AR Classification: STRONG, SUPPORTIVE, LIMITED Submitted by: PanelApp Australia, Orphanet, Ambry Genetics, Labcorp Genetics (formerly Invitae)

ACMG classification

Our verdict: Likely_benign. The variant received -1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.29).
• BP7: Synonymous conserved (PhyloP=1.05 with no splicing effect.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_016630.7. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	SPG21	NM_016630.7	MANE Select	c.819G>A	p.Leu273Leu	synonymous	Exon 9 of 9	NP_057714.1	Q9NZD8-1
	SPG21	NM_001127889.5		c.819G>A	p.Leu273Leu	synonymous	Exon 9 of 9	NP_001121361.1	Q9NZD8-1
	SPG21	NM_001127890.5		c.738G>A	p.Leu246Leu	synonymous	Exon 8 of 8	NP_001121362.1	Q9NZD8-2

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	SPG21	ENST00000204566.7	TSL:1 MANE Select	c.819G>A	p.Leu273Leu	synonymous	Exon 9 of 9	ENSP00000204566.2	Q9NZD8-1
	SPG21	ENST00000433215.6	TSL:1	c.819G>A	p.Leu273Leu	synonymous	Exon 9 of 9	ENSP00000404111.2	Q9NZD8-1
	SPG21	ENST00000854124.1		c.819G>A	p.Leu273Leu	synonymous	Exon 9 of 9	ENSP00000524183.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461314 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 727030

⚠️ 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: 33470

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26134

East Asian (EAS) AF: 0.00 AC: 0 AN: 39694

South Asian (SAS) AF: 0.00 AC: 0 AN: 86242

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53398

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5730

European-Non Finnish (NFE) AF: 9.00e-7 AC: 1 AN: 1111562

Other (OTH) AF: 0.00 AC: 0 AN: 60360

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 32

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.29
CADD	Benign	5.7
DANN	Benign	0.75
PhyloP100		1.1
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.060		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: rs2140402170; hg19: chr15-65256069;