Biallelic variants in CENPF causing a phenotype distinct from Strømme syndrome

Novel Loss of Function Variants in CENPF Including a Large Intragenic Deletion in Patients with Strømme Syndrome

Strømme syndrome is an ultra-rare primary ciliopathy with clinical variability. The syndrome is caused by bi-allelic variants in CENPF, a protein with key roles in both chromosomal segregation and ciliogenesis. We report three unrelated patients with Strømme syndrome and, using high-throughput sequencing approaches, we identified novel pathogenic variants in CENPF, including one structural variant, giving a genetic diagnosis to the patients. Patient 1 was a premature baby who died at 26 days with congenital malformations affecting many organs including the brain, eyes, and intestine. She was homozygous for a donor splice variant in CENPF, NM_016343.3:c.1068+1G>A, causing skipping of exon 7, resulting in a frameshift. Patient 2 was a female with intestinal atresia, microcephaly, and a Peters anomaly. She had normal developmental milestones at the age of 7 years. She is compound heterozygous for CENPF NM_016343.3:c.5920dup and c.8991del, both frameshift. Patient 3 was a male with anomalies of the brain, eye, intestine, and kidneys. He was compound heterozygous for CENPF p.(Glu298Ter), and a 5323 bp deletion covering exon 1. CENPF exon 1 is flanked by repetitive sequences that may represent a site of a recurrent structural variation, which should be a focus in patients with Strømme syndrome of unknown etiology.

Primary Cilia Influence Progenitor Function during Cortical Development

Corticogenesis is an intricate process controlled temporally and spatially by many intrinsic and extrinsic factors. Alterations during this important process can lead to severe cortical malformations. Apical neuronal progenitors are essential cells able to self-amplify and also generate basal progenitors and/or neurons. Apical radial glia (aRG) are neuronal progenitors with a unique morphology. They have a long basal process acting as a support for neuronal migration to the cortical plate and a short apical process directed towards the ventricle from which protrudes a primary cilium. This antenna-like structure allows aRG to sense cues from the embryonic cerebrospinal fluid (eCSF) helping to maintain cell shape and to influence several key functions of aRG such as proliferation and differentiation. Centrosomes, major microtubule organising centres, are crucial for cilia formation. In this review, we focus on how primary cilia influence aRG function during cortical development and pathologies which may arise due to defects in this structure. Reporting and cataloguing a number of ciliary mutant models, we discuss the importance of primary cilia for aRG function and cortical development.

Biallelic variants in CENPF causing a phenotype distinct from Strømme syndrome

Biallelic loss-of-function (LoF) variants in CENPF gene are responsible for Strømme syndrome, a condition presenting with intestinal atresia, anterior ocular chamber anomalies, and microcephaly. Through an international collaboration, four individuals (three males and one female) carrying CENPF biallelic variants, including two missense variants in homozygous state and four LoF variants, were identified by exome sequencing. All individuals had variable degree of developmental delay/intellectual disability and microcephaly (ranging from -2.9 SDS to -5.6 SDS) and a recognizable pattern of dysmorphic facial features including inverted-V shaped interrupted eyebrows, epicanthal fold, depressed nasal bridge, and pointed chin. Although one of the cases had duodenal atresia, all four individuals did not have the combination of internal organ malformations of Strømme syndrome (intestinal atresia and anterior eye segment abnormalities). Immunofluorescence analysis on skin fibroblasts on one of the four cases with the antibody for ARL13B that decorates primary cilia revealed shorter primary cilia that are consistent with a ciliary defect. This case-series of individuals with biallelic CENPF variants suggests the spectrum of clinical manifestations of the disorder that may be related to CENPF variants is broad and can include phenotypes lacking the cardinal features of Strømme syndrome.