Genetic Variant PHOX2B:p.Ala256Ala (chr4-41745984-T-G) – ACMG Classification: Likely_benign (-5 pts)

Variant summary

Our verdict is Likely benign. The variant received -5 ACMG points: 2P and 7B. PM2BP4_StrongBP6_ModerateBP7

The NM_003924.4(PHOX2B):c.768A>C(p.Ala256Ala) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000902 in 1,108,910 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Likely benign (★). Synonymous variant affecting the same amino acid position (i.e. A256A) has been classified as Likely benign.

Frequency

Genomes: not found (cov: 32)

Exomes 𝑓: 9.0e-7 ( 0 hom. )

Consequence

PHOX2B
NM_003924.4 synonymous

Scores

Clinical Significance

Likely benign criteria provided, single submitter B:1

Conservation

PhyloP100: -2.33

Variant links:

Genes affected

PHOX2B (HGNC:9143): (paired like homeobox 2B) The DNA-associated protein encoded by this gene is a member of the paired family of homeobox proteins localized to the nucleus. The protein functions as a transcription factor involved in the development of several major noradrenergic neuron populations and the determination of neurotransmitter phenotype. The gene product is linked to enhancement of second messenger-mediated activation of the dopamine beta-hydroylase, c-fos promoters and several enhancers, including cyclic amp-response element and serum-response element. Expansion of a 20 amino acid polyalanine tract in this protein by 5-13 aa has been associated with congenital central hypoventilation syndrome. [provided by RefSeq, Jul 2016]

PHOX2B links:

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ACMG classification

Classification was made for transcript

Our verdict: Likely_benign. The variant received -5 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

BP4

Computational evidence support a benign effect (BayesDel_noAF=-0.86).

BP6

Variant 4-41745984-T-G is Benign according to our data. Variant chr4-41745984-T-G is described in ClinVar as [Likely_benign]. Clinvar id is 3223599.Status of the report is criteria_provided_single_submitter, 1 stars.

BP7

Synonymous conserved (PhyloP=-2.33 with no splicing effect.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
PHOX2B	NM_003924.4 link	c.768A>C	p.Ala256Ala	synonymous_variant	Exon 3 of 3	ENST00000226382.4	NP_003915.2	Q99453

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
PHOX2B	ENST00000226382.4 link	c.768A>C	p.Ala256Ala	synonymous_variant	Exon 3 of 3	1	NM_003924.4	ENSP00000226382.2		Q99453
PHOX2B	ENST00000510424.2 link	n.*49A>C		downstream_gene_variant		3

Frequencies

GnomAD3 genomes

Cov.:

GnomAD4 exome

AF:

9.02e-7

AC:

AN:

1108910

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

533990

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:

22458

American (AMR)

AF:

0.00

AC:

AN:

9086

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

15326

East Asian (EAS)

AF:

0.00

AC:

AN:

23154

South Asian (SAS)

AF:

0.00

AC:

AN:

26230

European-Finnish (FIN)

AF:

0.00

AC:

AN:

29280

Middle Eastern (MID)

AF:

0.00

AC:

AN:

3120

European-Non Finnish (NFE)

AF:

0.00000107

AC:

AN:

936702

Other (OTH)

AF:

0.00

AC:

AN:

43554

⚠️ 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: 0.325

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

GnomAD4 genome

Cov.:

Alfa

AF:

0.00

Hom.:

Bravo

AF:

0.00000378

ClinVar

Significance: Likely benign

Submissions summary: Benign:1

Revision: criteria provided, single submitter

LINK: link

Submissions by phenotype

Hereditary cancer-predisposing syndrome

Benign:1

Dec 19, 2023

Ambry Genetics

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This alteration is classified as likely benign based on a combination of the following: seen in unaffected individuals, population frequency, intact protein function, lack of segregation with disease, co-occurrence, RNA analysis, in silico models, amino acid conservation, lack of disease association in case-control studies, and/or the mechanism of disease or impacted region is inconsistent with a known cause of pathogenicity. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_noAF

Benign

-0.86

CADD

Benign

3.0

(source)

DANN

Benign

0.29

PhyloP100

-2.3

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

Publications

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over