The phenotypic spectrum associated with OTX2 mutations in humans.

Objective: The transcription factor OTX2 is implicated in ocular, craniofacial, and pituitary development. Design: We aimed to establish the contribution of OTX2 mutations in congenital hypopituitarism patients with/without eye abnormalities, study functional consequences, and establish OTX2 expression in the human brain, with a view to investigate the mechanism of action. Methods: We screened patients from the UK (n = 103), international centres (n = 24), and Brazil (n = 282); 145 were within the septo-optic dysplasia spectrum, and 264 had no eye phenotype. Transactivation ability of OTX2 variants was analysed in murine hypothalamic GT1-7 neurons. In situ hybridization was performed on human embryonic brain sections. Genetically engineered mice were generated with a series of C-terminal OTX2 variants. Results: Two chromosomal deletions and six haploinsufficient mutations were identified in individuals with eye abnormalities; an affected relative of one patient harboured the same mutation without an ocular phenotype. OTX2 truncations led to significant transactivation reduction. A missense variant was identified in another patient without eye abnormalities; however, studies revealed it was most likely not causative. In the mouse, truncations proximal to aa219 caused anophthalmia, while distal truncations and the missense variant were tolerated. During human embryogenesis, OTX2 was expressed in the posterior pituitary, retina, ear, thalamus, choroid plexus, and partially in the hypothalamus, but not in the anterior pituitary. Conclusions: OTX2 mutations are rarely associated with hypopituitarism in isolation without eye abnormalities, and may be variably penetrant, even within the same pedigree. Our data suggest that the endocrine phenotypes in patients with OTX2 mutations are of hypothalamic origin.

Isolated absence of septum pellucidum: prenatal diagnosis and outcome.

Septal agenesis is a rare cerebral developmental anomaly characterized by partial or complete absence of the septum pellucidum (ASP). Septal agenesis may be associated with various congenital brain malformations, namely holoprosencephaly, septooptic dysplasia (SOD), schizencephaly or agenesis of the corpus callosum. Current imaging technologies do not enable differentiation in utero between isolated ASP and SOD. This is due to the fact that optic nerve hypoplasia and endocrine anomalies are never ruled out completely. We report a case of prenatal diagnosis of isolated ASP based on 2D and 3D ultrasound and fetal MRI. Postnatal MRI confirmed prenatal findings and the boy is currently doing well at 18 months of age.

[Natural course of septo-optic dysplasia: retrospective analysis of 20 cases]. / Evolucion natural de la displasia septooptica: analisis retrospectivo de 20 casos.

INTRODUCTION: Septo-optic dysplasia (SOD) is the variable combination of signs of dysgenesis of the midline of the brain, hypoplasia of the optic nerves and hypothalamus-pituitary dysfunction, which is sometimes associated with a varied spectrum of malformations of the cerebral cortex. AIMS: To describe the natural history and neuroimaging findings in a series of 20 diagnosed patients. PATIENTS AND METHODS: We review the epidemiological, clinical and neuroimaging characteristics of 20 consecutive patients diagnosed with SOD between January 1985 and January 2010. Data obtained from computerised tomography, magnetic resonance imaging of the head, electroencephalogram, visual evoked potentials, ophthalmological evaluation, karyotyping and endocrinological studies were analysed. In seven patients, a study of the gene Homeobox HESX1 was conducted. RESULTS: Pathological antecedents in the first three months of gestation were presented by 60% of the cases, with normal results in the foetal ultrasound scans. Clinically, the most striking features were visual manifestations (85%), endocrine disorders (50%), mental retardation (60%) and epileptic seizures (55%). Fifty-five per cent were associated to abnormal neuronal migration. In 45%, SOD was the only finding in the neuroimaging scans. Karyotyping was performed in all cases, the results being normal. Gene HESX1 was positive in two of the seven cases studied (both with isolated SOD). None of those with mutation in gene HESX1 presented familial consanguinity. No gene study was conducted with the parents. CONCLUSIONS: SOD must be classified as a heterogeneous malformation syndrome, which is associated to multiple brain, ocular, endocrine and systemic anomalies. The most severe forms are associated with abnormal neuronal migration and cortical organisation.

The syndrome of optic nerve hypoplasia.

The congenital malformation known as optic nerve hypoplasia (ONH) has been recognized in the past 30 years as an epidemic cause of congenital blindness. It was believed to occur either as an isolated anomaly or as a component of the syndrome of septo-optic dysplasia, which has evolved to include midline brain malformations and hypopituitarism. Evidence now suggests that ONH infrequently occurs in isolation. Most afflicted children will have hypothalamic dysfunction and/or neurodevelopmental impairment, regardless of MRI findings or severity of ONH. Adverse outcomes can often be ameliorated with early intervention. Thus, the syndrome of ONH should be suspected in all infants with signs of hypothalamic dysfunction or vision impairment.