Adele Schneider

Oculofaciocardiodental and Lenz microphthalmia syndromes result from distinct classes of mutations in BCOR.

Lenz microphthalmia is inherited in an X-linked recessive pattern and comprises microphthalmia, mental retardation, and skeletal and other anomalies. Two loci associated with this syndrome, MAA (microphthalmia with associated anomalies) and MAA2, are situated respectively at Xq27–q28 (refs. 1,2) and Xp11.4–p21.2 (ref. 3). We identified a substitution, nt 254C→T; P85L, in BCOR (encoding BCL-6-interacting corepressor, BCOR) in affected males from the family with Lenz syndrome previously used to identify the MAA2 locus. Oculofaciocardiodental syndrome (OFCD; OMIM 300166) is inherited in an X-linked dominant pattern with presumed male lethality and comprises microphthalmia, congenital cataracts, radiculomegaly, and cardiac and digital abnormalities. Given their phenotypic overlap, we proposed that OFCD and MAA2-associated Lenz microphthalmia were allelic, and we found different frameshift, deletion and nonsense mutations in BCOR in seven families affected with OFCD. Like wild-type BCOR, BCOR P85L and an OFCD-mutant form of BCOR can interact with BCL-6 and efficiently repress transcription. This indicates that these syndromes are likely to result from defects in alternative functions of BCOR, such as interactions with transcriptional partners other than BCL-6. We cloned the zebrafish (Danio rerio) ortholog of BCOR and found that knock-down of this ortholog caused developmental perturbations of the eye, skeleton and central nervous system consistent with the human syndromes, confirming that BCOR is a key transcriptional regulator during early embryogenesis.

SOX2 anophthalmia syndrome

Heterozygous, de novo, loss‐of‐function mutations in SOX2 have been shown to cause bilateral anophthalmia. Here we provide a detailed description of the clinical features associated with SOX2 mutations in the five individuals with reported mutations and four newly identified cases (including the first reported SOX2 missense mutation). The SOX2‐associated ocular malformations are variable in type, but most often bilateral and severe. Of the nine patients, six had bilateral anophthalmia and two had anophthalmia with contralateral microphthalmia with sclerocornea. The remaining case had anophthalmia with contralateral microphthalmia, posterior cortical cataract and a dysplastic optic disc, and was the only patient to have measurable visual acuity. The relatively consistent extraocular phenotype observed includes: learning disability, seizures, brain malformation, specific motor abnormalities, male genital tract malformations, mild facial dysmorphism, and postnatal growth failure. Identifying SOX2 mutations from large cohorts of patients with structural eye defects has delineated a new, clinically‐recognizable, multisystem disorder and has provided important insight into the developmental pathways critical for morphogenesis of the eye, brain, and male genital tract.

Expanded carrier screening in reproductive medicine-points to consider: a joint statement of the American College of Medical Genetics and Genomics, American College of Obstetricians and Gynecologists, National Society of Genetic Counselors, Perinatal Quality Foundation, and Society for Maternal-Fetal Medicine.

The Perinatal Quality Foundation and the American College of Medical Genetics and Genomics, in association with the American College of Obstetricians and Gynecologists, the Society for Maternal-Fetal Medicine, and the National Society of Genetic Counselors, have collaborated to provide education for clinicians and laboratories regarding the use of expanded genetic carrier screening in reproductive medicine. This statement does not replace current screening guidelines, which are published by individual organizations to direct the practice of their constituents. As organizations develop practice guidelines for expanded carrier screening, further direction is likely. The current statement demonstrates an approach for health care providers and laboratories who wish to or who are currently offering expanded carrier screening to their patients.

ACMG position statement on prenatal/preconception expanded carrier screening.

For years, clinicians have offered gene-by-gene carrier screening to patients and couples considering future pregnancy or those with an ongoing pregnancy early in gestation. Examples include ethnic-specific screening offered to Ashkenazi Jewish patients and panethnic screening for cystic fibrosis and spinal muscular atrophy. Next-generation sequencing methods now available permit screening for many more disorders with high fidelity, quick turnaround time, and lower costs. However, instituting these technologies carries with it perils that must be addressed. The basis for the selection of disorders on expanded carrier screening panels should be disclosed. The information provided about disorders with mild phenotypes, variable expression, low penetrance, and/or characterized by an adult onset should be complete and transparent, allowing patients to opt out of receiving these test results. Patients also must be made aware of the concept of residual risk following negative test results. Laboratories have a duty to participate in and facilitate this information transfer.Genet Med 2013:15(6):482–483

Novel SOX2 mutations and genotype-phenotype correlation in anophthalmia and microphthalmia.

SOX2 represents a High Mobility Group domain containing transcription factor that is essential for normal development in vertebrates. Mutations in SOX2 are known to result in a spectrum of severe ocular phenotypes in humans, also typically associated with other systemic defects. Ocular phenotypes include anophthalmia/microphthalmia (A/M), optic nerve hypoplasia, ocular coloboma and other eye anomalies. We screened 51 unrelated individuals with A/M and identified SOX2 mutations in the coding region of the gene in 10 individuals. Seven of the identified mutations are novel alterations, while the remaining three individuals carry the previously reported recurrent 20‐nucleotide deletion in SOX2, c.70del20. Among the SOX2‐positive cases, seven patients had bilateral A/M and mutations resulting in premature termination of the normal protein sequence (7/38; 18% of all bilateral cases), one patient had bilateral A/M associated with a single amino acid insertion (1/38; 3% of bilateral cases), and the final two patients demonstrated unilateral A/M associated with missense mutations (2/13; 15% of all unilateral cases). These findings and review of previously reported cases suggest a potential genotype/phenotype correlation for SOX2 mutations with missense changes generally leading to less severe ocular defects. In addition, we report a new familial case of affected siblings with maternal mosaicism for the identified SOX2 mutation, which further underscores the importance of parental testing to provide accurate genetic counseling to families.

OTX2 microphthalmia syndrome: four novel mutations and delineation of a phenotype

Schilter KF, Schneider A, Bardakjian T, Soucy J‐F, Tyler RC, Reis LM, Semina EV. OTX2 microphthalmia syndrome: four novel mutations and delineation of a phenotype.

Role of SOX2 mutations in human hippocampal malformations and epilepsy

Summary:  Purpose: Seizures are noted in a significant proportion of cases of de novo, heterozygous, loss‐of‐function mutations in SOX2, ascertained because of severe bilateral eye malformations. We wished to determine the underlying cerebral phenotype in SOX2 mutation and to test the candidacy of SOX2 as a gene contributing to human epilepsies.

BMP4 loss-of-function mutations in developmental eye disorders including SHORT syndrome

BMP4 loss-of-function mutations and deletions have been shown to be associated with ocular, digital, and brain anomalies, but due to the paucity of these reports, the full phenotypic spectrum of human BMP4 mutations is not clear. We screened 133 patients with a variety of ocular disorders for BMP4 coding region mutations or genomic deletions. BMP4 deletions were detected in two patients: a patient affected with SHORT syndrome and a patient with anterior segment anomalies along with craniofacial dysmorphism and cognitive impairment. In addition to this, three intragenic BMP4 mutations were identified. A patient with anophthalmia, microphthalmia with sclerocornea, right-sided diaphragmatic hernia, and hydrocephalus was found to have a c.592C>T (p.R198X) nonsense mutation in BMP4. A frameshift mutation, c.171dupC (p.E58RfsX17), was identified in two half-siblings with anophthalmia/microphthalmia, discordant developmental delay/postaxial polydactyly, and poor growth as well as their unaffected mother; one affected sibling carried an additional BMP4 mutation in the second allele, c.362A>G (p.H121R). This is the first report indicating a role for BMP4 in SHORT syndrome, Axenfeld–Rieger malformation, growth delay, macrocephaly, and diaphragmatic hernia. These results significantly expand the number of reported loss-of-function mutations, further support the critical role of BMP4 in ocular development, and provide additional evidence of variable expression/non-penetrance of BMP4 mutations.

Loss of the BMP Antagonist, SMOC-1, Causes Ophthalmo-Acromelic (Waardenburg Anophthalmia) Syndrome in Humans and Mice

Ophthalmo-acromelic syndrome (OAS), also known as Waardenburg Anophthalmia syndrome, is defined by the combination of eye malformations, most commonly bilateral anophthalmia, with post-axial oligosyndactyly. Homozygosity mapping and subsequent targeted mutation analysis of a locus on 14q24.2 identified homozygous mutations in SMOC1 (SPARC-related modular calcium binding 1) in eight unrelated families. Four of these mutations are nonsense, two frame-shift, and two missense. The missense mutations are both in the second Thyroglobulin Type-1 (Tg1) domain of the protein. The orthologous gene in the mouse, Smoc1, shows site- and stage-specific expression during eye, limb, craniofacial, and somite development. We also report a targeted pre-conditional gene-trap mutation of Smoc1 (Smoc1tm1a) that reduces mRNA to ∼10% of wild-type levels. This gene-trap results in highly penetrant hindlimb post-axial oligosyndactyly in homozygous mutant animals (Smoc1tm1a/tm1a). Eye malformations, most commonly coloboma, and cleft palate occur in a significant proportion of Smoc1tm1a/tm1a embryos and pups. Thus partial loss of Smoc-1 results in a convincing phenocopy of the human disease. SMOC-1 is one of the two mammalian paralogs of Drosophila Pentagone, an inhibitor of decapentaplegic. The orthologous gene in Xenopus laevis, Smoc-1, also functions as a Bone Morphogenic Protein (BMP) antagonist in early embryogenesis. Loss of BMP antagonism during mammalian development provides a plausible explanation for both the limb and eye phenotype in humans and mice.

Analysis of the developmental SIX6 homeobox gene in patients with anophthalmia/microphthalmia

SIX6 is a recently characterized member of the SIX/sine oculis family of homeobox genes that is expressed in the developing and adult retina, in the optic nerve and in the hypothalamic and pituitary regions [Gallardo et al., 1999; Rodrı́guez de Córdoba et al., 2001]. SIX6maps to chromosome 14q22.3q23, a region that is deleted in three individuals with bilateralanophthalmiaandpituitaryanomalies [Bennett etal., 1991; Elliott et al., 1993; Lemyre et al., 1998]. In one of these cases [Bennett et al., 1991], the deletion includes the SIX6 gene, supporting the notion that the ocular and pituitary phenotype in this individual could be caused by SIX6 haploinsufficiency and that SIX6 is a candidate gene for anophthalmia [Gallardo et al., 1999]. Moreover, disruption of the Six6 gene in mice causes pituitary gland and retinal anomalies, often with absence of optic chiasm and optic nerve, resembling the human phenotype [Li et al., 2002]. To evaluate whether the homeobox SIX6 gene is a cause of human eye malformations, we have collected European pedigrees with syndromic or non-syndromic sporadic anophthalmia/ microphthalmia (A/M) and tested them for mutations in SIX6. Patientswere included in the studybased on the only criteria of presenting microphthalmia or anophthalmia. Thirty-six patients are from the A/M Registry at Albert Einstein Medical Center (Philadelphia) and are part of a broad survey of genetic eye disease. The remaining 37 were provided by the Department of Genetics at the Hospital Fundación Jiménez Dı́az (Madrid). DNA from these 73 patients and their relatives was obtained with informed consent following protocols approved by the Institucional Review Boards for human subjects at Albert Einstein Medical Center and Fundación Jiménez Dı́az. Each exon of the SIX6 gene was amplified from genomic DNA of patients and controls using specific primers derived from the 50and 30-intronic sequences. The sequence of these primers and the PCR conditions used for the amplifications are describedelsewhere [Gallardo et al., 1999;Rodrı́guezdeCórdobaetal., 2001]. Direct sequencing of PCRproductswas performed semiautomatically inboth strands inanABI3700 sequencerusinga dye terminator cycle sequencing kit (Applied Biosystems, Foster City, CA, USA). We have identified four single nucleotide changes compared to the reference SIX6 sequence (accession number: NM_007374) [Gallardo et al., 1999]. Analysis of these nucleotide substitution in a sample of 78 chromosomes from normal individuals demonstrated that three of them [IVS1-185A>G, c.21G>A (L7L), and c.421A>C (N141H)] are frequent single nucleotidepolymorphisms (SNPs) in thehumanSIX6geneand shownoassociationwith theA/Mphenotype (Fig. 1, Table I). In addition to these three polymorphic sites, we report the identification of a patient with a heterozygous amino acid substitution (c.493A>G; T165A) in exon 1 of SIX6 (Fig. 2). The alterationwasnot found in a control population includingmore than 160 chromosomes from normal individuals. The patient carrying the T165A alteration is an 18-year-old female. The patient presented with congenital bilateral asymmetric microphthalmia, cataract, nistagmus, and syndactyly of toes 2/3. At 1 year of age, she underwent cataract extraction onher left eye. Subsequently, she developed secondary glaucoma in this eye. At 5 years of age, she had visual acuity of hand movement in her right eye and amaurosis in her left eye. Due to the lens opacities and the small size of the globes, eye fundi were very difficult to exam. As glaucoma progressed, the left eye was surgically removed at 7 years of age and replaced by a prosthetic eye. At 11 years of age, growth and psychomotor development were normal. Neurological examination and brainMRIwere also normal,with no abnormalities of posterior pituitary gland. Ocular examination at this age showed microphthalmia, cataract, and nystagmus in the right eye with 20/400 visual acuity and a prosthetic left eye. Ultrasonographic biomicroscopy demonstrated a large cyst in the right eye. Her karyotype is normal. She was born to non-consanguineous parents. Ophthamological examinations of the parents revealed normal ocular development and visual acuity. Isolated syndactyly of toes 2/3 is a very frequent minor limb anomaly that we consider unrelated to the ocular phenotype of the patient. Mutations in other genes associated with microphthalmia, like CHX10 [Percin et al., 2000], were excluded in this patient (data not shown). The alteration changes a