MACF1 Mutations Encoding Highly Conserved Zinc-Binding Residues of the GAR Domain Cause Defects in Neuronal Migration and Axon Guidance

To date, mutations in 15 actin- or microtubule-associated genes have been associated with the cortical malformation lissencephaly and variable brainstem hypoplasia. During a multicenter review, we recognized a rare lissencephaly variant with a complex brainstem malformation in three unrelated children. We searched our large brain-malformation databases and found another five children with this malformation (as well as one with a less severe variant), analyzed available whole-exome or -genome sequencing data, and tested ciliogenesis in two affected individuals. The brain malformation comprised posterior predominant lissencephaly and midline crossing defects consisting of absent anterior commissure and a striking W-shaped brainstem malformation caused by small or absent pontine crossing fibers. We discovered heterozygous de novo missense variants or an in-frame deletion involving highly conserved zinc-binding residues within the GAR domain of MACF1 in the first eight subjects. We studied cilium formation and found a higher proportion of mutant cells with short cilia than of control cells with short cilia. A ninth child had similar lissencephaly but only subtle brainstem dysplasia associated with a heterozygous de novo missense variant in the spectrin repeat domain of MACF1. Thus, we report variants of the microtubule-binding GAR domain of MACF1 as the cause of a distinctive and most likely pathognomonic brain malformation. A gain-of-function or dominant-negative mechanism appears likely given that many heterozygous mutations leading to protein truncation are included in the ExAC Browser. However, three de novo variants in MACF1 have been observed in large schizophrenia cohorts.

Phenotypic and molecular insights into PQBP1-related intellectual disability

We report two discordant clinical and imaging features in four male patients from two unrelated families of Egyptian descent with hemizygous pathogenic variants in PQBP1. The three patients of the first family displayed the typical features underlying PQBP1 such as the long triangular face, bulbous nose, hypoplastic malar region, and micrognathia, which were subsequently confirmed using targeted sequence analysis that showed a previously reported nonsense mutation c.586C>T p.R196*. Whole exome sequencing identified a novel missense PQBP1 variant c.530G>A:p.R177H in the second family, in which the index patient presented with intellectual disability and dysmorphic facial features reminiscent of Kabuki-like syndrome and his brain magnetic resonance imaging revealed partial agenesis of corpus callosum, mild vermis, and brainstem hypoplasia. These imaging features are distinct from the previously described with a well-known phenotype that is already known for PQBP1. This report expands the phenotypic spectrum of PQBP1-related disorders and is the second reported missense PQBP1 variant. Further, it highlights the possible role of PQBP1 in hindbrain development.

Clinical and surgical management of a congenital Type II split cord malformation presenting with progressive cranial neuropathies: case report

Split cord malformation (SCM) is a rare abnormality of notochord development. The majority of cases occur in the thoracolumbar region, with more than 30 cases of cervical SCM reported. The clinical impact of SCMs involving the cervical cord is therefore largely unknown. In addition, the concomitant finding of brainstem involvement is presumably incompatible with life in the majority of patients, resulting in a paucity of data regarding this clinical scenario. In this paper the authors present the first case, to their knowledge, of an incomplete cervical SCM involving the brainstem and discuss its clinical impact, diagnosis, and management.

Clinical characteristics and outcomes of Möbius syndrome in a children's hospital

BACKGROUND

Möbius syndrome is a congenital disorder with facial and abducens palsy. Although a few case series studies have examined comorbid conditions in Möbius syndrome, follow-up and outcome data are sparse.

OBJECTIVES

To examine the clinical characteristics and outcomes of Möbius syndrome.

METHODS

Clinical data were reviewed for 10 patients. Neonatal history, neurological examination, comorbid anomalies, medical home care, outcomes, and neuroimaging were summarized.

RESULTS

The patients' mean age was 7.3 ± 6.2 years. On neurological examination, absent blink reflex, jaw ankylosis, absent gag reflex, and tongue atrophy were frequently observed. Poland anomaly and clubfoot were present in three and six patients, respectively. Specific therapies required for patients included medical home care (six patients), suction apparatus (six), tube feeding (five), gastrostomy (two), tracheostomy (three), oxygen therapy (three), and home ventilator (two). Punctate calcification in the brainstem was observed in four patients. Pontine and medulla hypoplasia were detected on the basis of anteroposterior diameter in four and seven patients, respectively. Two patients had congenital hydrocephalus with aqueductal stenosis. Global developmental delay occurred in five patients. Three patients died.

CONCLUSION

The rate of both the use of home medical devices and death was high in our patients. Möbius syndrome is extremely diverse, not only in clinical manifestation, but also outcome. Early multidisciplinary intervention is important to ensure an optimal outcome. Aqueductal stenosis is an occasional comorbid anomaly resulting from midbrain abnormality.

Pontine malformation, undecussated pyramidal tracts, and regional polymicrogyria: a new syndrome

BACKGROUND

Horizontal gaze palsy and progressive scoliosis is caused by mutations in the ROBO3 gene, which plays a role in axonal guidance during brain development. Horizontal gaze palsy and progressive scoliosis is characterized by the congenital absence of conjugate lateral eye movements with preserved vertical gaze and progressive scoliosis as well as dysgenesis of brainstem structures and ipsilateral projection of the pyramidal tract.

PATIENT

A 4-year, 11-month, girl presented with psychomotor retardation and autistic traits. Magnetic resonance imaging revealed hypoplasia and malformation of the ventral portion of the pons and medulla oblongata. Diffusion tensor imaging revealed the absence of decussation of the bilateral pyramidal tracts. These findings were similar to the typical findings for horizontal gaze palsy and progressive scoliosis. However, restriction of horizontal eye movement was minimal, and bilateral polymicrogyria were also noted in the occipitotemporal cortex in the present patient. These findings have not been previously reported in patients with horizontal gaze palsy and progressive scoliosis. No mutations in the ROBO3, SLIT1, SLIT2, NTN1, SEMA3 A, or SEMA3 F genes were identified.

CONCLUSION

This child may have a disorder caused by an unidentified factor, other than a mutation in the genes analyzed, involved in corticogenesis, axonal guidance, and brainstem morphogenesis.