BCOR gene

• Overview
• Microphthalmia, anophthalmia, coloboma (MAC)
• Congenital cataract
• Additional information
• References

Overview

Gene (OMIM No.)	BCOR (#300485)
Function of gene/protein	Protein: BCL6 compressor Interacts with other DNA-binding proteins to suppress the activity of certain genes Plays a critical role in early embryonic development, including the eye Regulates B and T-cell development and prevents oncogenesis of these cells
Clinical phenotype (OMIM phenotype no.)	Microphthalmia, syndromic 2 (#300166) Also known as oculofacialcardiodental (OFCD) syndrome X-linked recessive microphthalmia, syndromic 1 (also known as Lenz microphthalmia syndrome #309800) has been reported with a missense BCOR variant (p.Pro85Leu)
Inheritance	X-linked dominant X-linked recessive in some cases
Ocular features	Microphthalmia, anophthalmia, coloboma (MAC) spectrum Congenital cataract (consistent feature in OFCD syndrome)
Systemic features	X-linked dominant microphthalmia, syndromic 2 (OFCD syndrome): Usually in females due to presumed in utero male lethality Facial (distinctive facial features, including deep-set eyes and a broad nasal tip that is divided by a cleft) Cardiac (atrial and ventricular septal defect) Dental (radiculomegaly, persistent primary teeth, misaligned, missing or abnormally small teeth and defective tooth enamel) Skeletal (hammer toes, second-third toe syndactyly, limited supination of wrist from radioulnar synostosis and fixed flexion deformity of the fifth proximal interphalangeal joints usually) X-linked recessive microphthalmia, syndromic 1 (Lenz microphthalmia syndrome) Hemizygous males with the p.Pro85Leu variant Overlapping features with OFCD but no dental anomalies Craniofacial (microcephaly, narrow forehead, midface hypoplasia and simple ears) Cardiac (atrial and ventricular septal defect) Skeletal (limited supination of wrist, multiple partial finger syndactyly, fifth finger clinodactyly) Genitourinary (hypospadias, cryptorchidism, renal dysplasia) Mild to severe developmental delays
Key investigations	B-scan USS to measure axial length to document microphthalmia and detect any posterior abnormalities in congenital cataract cases Electrophysiology TORCH screen for children with congenital cataract MRI brain and orbit Systemic assessment with a paediatrician and other relevant specialists
Molecular diagnosis	Next generation sequencing Targeted gene panels (MAC and/or cataract) Whole genome sequencing
Management	Ocular Management of MAC Management of congenital cataract Systemic Multidisciplinary approach
Therapies under research	None at present
Further information	Medline Plus

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Additional information

Oculofacialcardiodental (OFCD) syndrome and Lenz microphthalmia form part of a spectrum of syndromic microphthalmia due to pathogenic variants in BCOR.

1) OFCD syndrome/Microphthalmia, syndromic 2 (MCOPS2)

Null mutations of BCOR result in this phenotype. It is mainly characterised by congenital cataract and microphthalmia with facial, cardiac and dental anomalies. Not all patients will present with anomalies in all four categories. Skeletal anomalies are frequently observed in addition to these classical characteristics. Other reported features include:

• Mild developmental delays
• Hearing impairment
• Poor feeding/vomiting/reflux
• Laterality defects of the heart and viscera
• Neuropathy/muscle hypotonia
• Pituitary underdevelopment
• Lipoma
• Childhood lymphoma reported in 1 case^[3]

2) X-linked recessive Lenz microphthalmia syndrome/microphthalmia, syndromic 1 (MCOPS1)  

A missense mutation causing the substitution of the conserved amino acid proline into leucine at position 85 (p.Pro85Leu) result in severe microphthalmia or anophthalmia in hemizygous males with systemic features that partially overlaps with OFCD. These include craniofacial, cardiac and skeletal anomalies while no dental anomalies have been reported with this variant so far.

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References

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