SIX3

protein-coding

SIX homeobox 3, the group of SINE class homeoboxes

Gene summary

This gene encodes a member of the sine oculis homeobox transcription factor family. The encoded protein plays a role in eye development. Mutations in this gene have been associated with holoprosencephaly type 2. [provided by RefSeq, Oct 2009]

Previous symbols:
  • HPE2

MANE transcript

NM_005413.4

Inheritance

AD

ClinVar variants

P:36U:133B:82

Top phenotype

Holoprosencephaly 2

gnomAD constraint

pLI —, LoF o/e 0

Max pathogenic AF

—

Genomic locus

chr2:44,941,702-44,946,071

External References & Databases

Transcript & Mutation Effects

hg38 • Region Span ~4.4 kb
Loading mutation effect viewer...

GenCC Phenotypes & Disease Associations

Curated gene-disease validity assertions and inheritance patterns

holoprosencephaly 2STRONG

Inheritance Pattern: AD

Disease ID:MONDO:0007999

Submitter: Labcorp Genetics (formerly Invitae)

holoprosencephaly 2STRONG

Inheritance Pattern: AD

Disease ID:MONDO:0007999

Submitter: PanelApp Australia

holoprosencephaly 2DEFINITIVE

Inheritance Pattern: AD

Disease ID:MONDO:0007999

Submitter: G2P

holoprosencephaly 2STRONG

Inheritance Pattern: AD

Disease ID:MONDO:0007999

Submitter: Laboratory for Molecular Medicine

This gene-disease relationship has undergone rapid assessment. Classifications are based on preliminary review of gene-disease validity during analysis of genomic sequencing results.

Clinical Genomic Database (CGD)

Holoprosencephaly 2AD

Manifestation: Craniofacial; Endocrine; Neurologic; Ophthalmologic

Intervention: General

Rationale: Genetic knowledge may be beneficial related to issues such as selection of optimal supportive care, informed medical decision-making, prognostic considerations, and avoidance of unnecessary testing

Comments: Variants in SIX3 have also been implicated in schizencephaly, but the data are unclear, and this may have co-occurred with typical holoprosencephaly-type malformations; Individuals with holoprosencephaly may demonstrate endocrine anomalies

Refs: 10369266; 15221788; 16199538; 17001667; 19346217; 19353631; 20157829; 20531442; 21940735; 21976454; 23112757Source: CGD (NHGRI)

ClinVar Associated Diseases & Phenotypes

Reported disease conditions connected to SIX3 variants in ClinVar

8 Conditions Cataloged
Holoprosencephaly 2Total: 154
not providedTotal: 103
Inborn genetic diseasesTotal: 46
not specifiedTotal: 32
SIX3-related disorderTotal: 27
SchizencephalyTotal: 10
Solitary median maxillary central incisor syndromeTotal: 1
Intellectual disabilityTotal: 1

ClinVar Variants & Pathogenicity by Type

Statistics based on transcript NM_005413.4. Only rare variants are included.

We include only reliable ClinVar variants with their consequences to MANE Select, MANE Plus Clinical transcripts, or transcripts with TSL equal to 1. Click a count to filter the variants table below.

Slight differences between displayed counts and ClinVar may occur due to a different transcript/consequence chosen by our variant effect predictor, or because we classify Benign/Likely benign as Likely benign and Pathogenic/Likely pathogenic as Likely pathogenic.

EffectPLPVUSLBBSum
synonymous
5
clinvar
73
clinvar
1
clinvar
79
missense
4
clinvar
7
clinvar
127
clinvar
6
clinvar
2
clinvar
146
nonsense
6
clinvar
2
clinvar
8
start loss
1
clinvar
1
frameshift
9
clinvar
5
clinvar
1
clinvar
15
splice donor/acceptor (+/-2bp)
1
clinvar
1
clinvar
2
Total2016133793251

Highest pathogenic variant AF is 0.0000055398823

Loading ClinVar variants...

Transcript Catalog

Annotated transcript isoforms across RefSeq and Ensembl databases

Showing 3 of 3 transcripts
Transcript IDSourceProtein IDCoding ExonsMANE Status
NM_005413.4RefSeqNP_005404.12MANE Select
ENST00000260653.5EnsemblENSP00000260653.32MANE Select
ENST00001145412.1EnsemblENSP00000803069.12Standard

Gene Ontology (GO) Annotations & Pathways

Biological processes, molecular functions, cellular components and pathways

Pathways ConsensusPathDB

  • Preimplantation Embryo

Biological Process

  • obsolete protein import into nucleus, translocation
  • eye development
  • epithelial cell maturation
  • lens development in camera-type eye
  • optic vesicle morphogenesis

Molecular Function

  • transcription regulatory region sequence-specific DNA binding
  • RNA polymerase II distal enhancer sequence-specific DNA binding
  • DNA-binding transcription factor activity, RNA polymerase II-specific
  • transcription corepressor binding
  • DNA-binding transcription factor activity

Cellular Component

  • nucleus
  • transcription factor complex

gnomAD Constraint

Source: gnomAD

Gene type
protein_coding
Transcript type
protein_coding
Transcript
ENST00000260653
Coding exons
2
Length
4315
Individuals with no LoFs
117557
Homozygous LoFs
0
Heterozygous LoFs
2
Defined
117559
p
0.00000851
Z-ScoreObservedExpectedObserved/ExpectedMutation RateTotal Possible
Missense2.071192020.5890.000009352093
Missense (PolyPhen)2266.4810.33092684
Synonymous-1.8711289.51.250.00000429691
Loss of Function2.8209.270.004.01e-798

Population LoF Frequency

PopulationCAFp-valueStatus
African00.0absent
Latino/Admixed American0.0000580.000058rare
Ashkenazi Jewish00.0absent
East Asian00.0absent
Finnish00.0absent
European (Non-Finnish)00.0absent
South Asian00.0absent
Other00.0absent

dbNSFP Gene Annotations

Source: dbNSFP

Function
FUNCTION: Transcriptional regulator which can act as both a transcriptional repressor and activator by binding a ATTA homeodomain core recognition sequence on these target genes. During forebrain development represses WNT1 expression allowing zona limitans intrathalamica formation and thereby ensuring proper anterio-posterior patterning of the diencephalon and formation of the rostral diencephalon. Acts as a direct upstream activator of SHH expression in the rostral diencephalon ventral midline and that in turn SHH maintains its expression. In addition, Six3 activity is required for the formation of the telencephalon. During postnatal stages of brain development is necessary for ependymal cell maturation by promoting the maturation of radial glia into ependymal cells through regulation of neuroblast proliferation and migration. Acts on the proliferation and differentiation of neural progenitor cells through activating transcription of CCND1 AND CCND2. During early lens formation plays a role in lens induction and specification by activating directly PAX6 in the presumptive lens ectoderm. In turn PAX6 activates SIX3 resulting in activation of PDGFRA and CCND1 promoting cell proliferation. Also is required for the neuroretina development by directly suppressing WNT8B expression in the anterior neural plate territory. Its action during retina development and lens morphogenesis is AES and TLE4-dependent manner. Furthermore, during eye development regulates several genes expression. Before and during early lens development represses the CRYGF promoter by binding a SIX repressor element. Directly activates RHO transcription, or cooperates with CRX or NRL. Six3 functions also in the formation of the proximodistal axis of the optic cup, and promotes the formation of optic vesicles-like structures. During pituitary development, acts in parallel or alternatively with HESX1 to control cell proliferation through Wnt/beta-catenin pathway (By similarity). Plays a role in eye development by suppressing WNT1 expression and in dorsal- ventral patterning by repressing BMP signaling pathway. {ECO:0000250|UniProtKB:Q62233, ECO:0000269|PubMed:18791198}.;
Disease
DISEASE: Holoprosencephaly 2 (HPE2) [MIM:157170]: A structural anomaly of the brain, in which the developing forebrain fails to correctly separate into right and left hemispheres. Holoprosencephaly is genetically heterogeneous and associated with several distinct facies and phenotypic variability. {ECO:0000269|PubMed:10369266, ECO:0000269|PubMed:15221788, ECO:0000269|PubMed:15523651, ECO:0000269|PubMed:17001667, ECO:0000269|PubMed:18791198, ECO:0000269|PubMed:20531442}. Note=The disease is caused by mutations affecting the gene represented in this entry.; DISEASE: Schizencephaly (SCHZC) [MIM:269160]: Extremely rare human congenital disorder characterized by a full-thickness cleft within the cerebral hemispheres. These clefts are lined with gray matter and most commonly involve the parasylvian regions. Large portions of the cerebral hemispheres may be absent and replaced by cerebro- spinal fluid. {ECO:0000269|PubMed:20157829}. Note=The disease is caused by mutations affecting the gene represented in this entry.;

Recessive Scores

pRec
0.218

Intolerance Scores

LoFtool
0.0812
RVIS EVS
0.06
RVIS percentile EVS
58.26

Essentials

Essential (CRISPR)
N
Essential (CRISPR2)
N
Essential (gene trap)
N
Indispensability pred.
E
Indispensability score
0.958

Gene Damage Prediction

AllRecessiveDominant
MendelianMediumMediumMedium
Primary ImmunodeficiencyMediumMediumMedium
CancerMediumMediumMedium
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