rs1555756363

Variant names:

• chr19-41357947-GC-TT
• rs1555756363
• NM_030578.4:c.163_164delGCinsAA

Variant summary

Our verdict is Uncertain significance. The variant received 3 ACMG points: 3P and 0B. PM1 PP3

The NM_030578.4(B9D2):​c.163_164delGCinsAA​(p.Ala55Asn) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. The variant is present in control chromosomes in GnomAd MNV project. The variant allele was found at a frequency of 0.00000707 in 2 alleles, including 0 homozygotes. It is difficult to determine the true allele frequency of this variant because it is of type MNV, and the frequency of such variant types in population databases may be underestimated and unreliable. 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. A55D) has been classified as Uncertain significance.

• Frequency: GnomAD MNV: 𝑓 0.0000071 Genomes: not found (cov: 31)
• Consequence: B9D2 NM_030578.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 8.88
• Publications: 0 publications found

Genes affected

B9D2 (HGNC:28636): (B9 domain containing 2) This gene encodes a B9 domain protein, which are exclusively found in ciliated organisms. The gene is upregulated during mucociliary differentiation, and the encoded protein localizes to basal bodies and cilia. Disrupting expression of this gene results in ciliogenesis defects. [provided by RefSeq, Oct 2009]

TMEM91 (HGNC:32393): (transmembrane protein 91) Predicted to act upstream of or within hematopoietic progenitor cell differentiation. Predicted to be integral component of membrane. Predicted to be active in intracellular membrane-bounded organelle and membrane. [provided by Alliance of Genome Resources, Apr 2022]

ENSG00000255730 (HGNC:):

ACMG classification

Our verdict: Uncertain_significance. The variant received 3 ACMG points.

• PM1: In a chain B9 domain-containing protein 2 (size 174) in uniprot entity B9D2_HUMAN there are 6 pathogenic changes around while only 2 benign (75%) in NM_030578.4
• PP3: No computational evidence supports a deleterious effect, but strongly conserved according to phyloP

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_030578.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	B9D2	NM_030578.4	MANE Select	c.163_164delGCinsAA	p.Ala55Asn	missense	N/A	NP_085055.2

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	B9D2	ENST00000243578.8	TSL:1 MANE Select	c.163_164delGCinsAA	p.Ala55Asn	missense	N/A	ENSP00000243578.2
	TMEM91	ENST00000539627.5	TSL:1	c.-30+6745_-30+6746delGCinsTT		intron	N/A	ENSP00000441900.1
	B9D2	ENST00000675972.1		c.163_164delGCinsAA	p.Ala55Asn	missense	N/A	ENSP00000501911.1

Frequencies

GnomAD3 genomes Cov.: 31

We have no GnomAD4 exomes data on this position. Probably position not covered by the project.

GnomAD4 genome Cov.: 31

GnomAD MNV AF: 0.00000707 AC: 2 Hom.: 0

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Meckel-Gruber syndrome;C0431399:Joubert syndrome Uncertain:1

Apr 11, 2017

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change deletes 2 nucleotides and inserts 2 nucleotides in exon 3 of the B9D2 mRNA (c.163_164delinsAA), replacing alanine with asparagine at codon 55 of the B9D2 protein (p.Ala55Asn). The alanine residue is highly conserved and there is a moderate physicochemical difference between alanine and asparagine. This variant is reported as two separate single-nucleotide changes in the ExAC database (c.163G>A and c.164C>A), but the read data shows that the two variants are in cis, recapitulating the variant observed here (c.163_164delinsAA), in 2 individuals. It has not been reported in the literature in individuals with a B9D2-related disease Algorithms developed to predict the effect of missense changes on protein structure and function do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0"). In summary, this variant is a rare missense change with uncertain impact on protein function. There is no indication that it causes disease, but the available evidence is currently insufficient to prove that conclusively. Therefore, it has been classified as a Variant of Uncertain Significance.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
PhyloP100		8.9

Splicing

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs1555756363; hg19: chr19-41863852;