Genetic Variant KNL1:c.76-4C>G (chr15-40606389-C-G) – ACMG Classification: Likely_benign (-2 pts)

Variant summary

Our verdict is Likely benign. The variant received -2 ACMG points: 2P and 4B. PM2BP4_Strong

The NM_144508.5(KNL1):c.76-4C>G variant causes a splice region, intron change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000721 in 1,387,322 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 3/3 splice prediction tools predict no significant impact on normal splicing. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar.

Frequency

Genomes: not found (cov: 32)

Exomes 𝑓: 7.2e-7 ( 0 hom. )

Consequence

KNL1
NM_144508.5 splice_region, intron

Scores

Splicing: ADA: 0.0003857

Clinical Significance

Not reported in ClinVar

Conservation

PhyloP100: -0.0510

Publications

0 publications found

Variant links:

Genes affected

KNL1 (HGNC:24054): (kinetochore scaffold 1) The protein encoded by this gene is a component of the multiprotein assembly that is required for creation of kinetochore-microtubule attachments and chromosome segregation. The encoded protein functions as a scaffold for proteins that influence the spindle assembly checkpoint during the eukaryotic cell cycle and it interacts with at least five different kinetochore proteins and two checkpoint kinases. In adults, this gene is predominantly expressed in normal testes, various cancer cell lines and primary tumors from other tissues and is ubiquitously expressed in fetal tissues. This gene was originally identified as a fusion partner with the mixed-lineage leukemia (MLL) gene in t(11;15)(q23;q14). Mutations in this gene cause autosomal recessive primary microcephaly-4 (MCPH4). Alternative splicing results in multiple transcript variants encoding different isoforms. Additional splice variants have been described but their biological validity has not been confirmed. [provided by RefSeq, Jan 2013]

KNL1 Gene-Disease associations (from GenCC):

microcephaly 4, primary, autosomal recessive
Inheritance: AR Classification: STRONG, MODERATE Submitted by: Ambry Genetics, Labcorp Genetics (formerly Invitae)
autosomal recessive primary microcephaly
Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

KNL1 links:

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ACMG classification

Classification was made for transcript

Our verdict: Likely_benign. The variant received -2 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

BP4

Computational evidence support a benign effect (BayesDel_noAF=-0.87).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
KNL1	NM_144508.5 link	c.76-4C>G		splice_region_variant, intron_variant	Intron 3 of 25	ENST00000399668.7	NP_653091.3	Q8NG31-2
KNL1	NM_170589.5 link	c.76-4C>G		splice_region_variant, intron_variant	Intron 3 of 26		NP_733468.3	Q8NG31-1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
KNL1	ENST00000399668.7 link	c.76-4C>G		splice_region_variant, intron_variant	Intron 3 of 25	1	NM_144508.5	ENSP00000382576.3		Q8NG31-2

Frequencies

GnomAD3 genomes

Cov.:

GnomAD4 exome

AF:

7.21e-7

AC:

AN:

1387322

Hom.:

Cov.:

AF XY:

0.00000144

AC XY:

AN XY:

693676

show subpopulations

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

African (AFR)

AF:

0.00

AC:

AN:

32142

American (AMR)

AF:

0.00

AC:

AN:

44460

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

25498

East Asian (EAS)

AF:

0.00

AC:

AN:

39338

South Asian (SAS)

AF:

0.00

AC:

AN:

84224

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53238

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5434

European-Non Finnish (NFE)

AF:

9.57e-7

AC:

AN:

1045192

Other (OTH)

AF:

0.00

AC:

AN:

57796

⚠️ 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.

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.225

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

GnomAD4 genome

Cov.:

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_noAF

Benign

-0.87

CADD

Benign

3.0

(source)

DANN

Benign

0.53

PhyloP100

-0.051

Splicing

Name

Calibrated prediction

Score

Prediction

dbscSNV1_ADA

Benign

0.00039

dbscSNV1_RF

Benign

0.046

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

Publications

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Computational scores

Splicing

Publications

Other links and lift over