RESUMEN
Primrose syndrome is a rare autosomal dominant disorder that is characterized by recognizable facial phenotype, sensorineural hearing loss, hypotonia, and developmental delay. All reported probands show de novo ZBTB20 pathogenic variant. Since its discovery in 1982, Primrose syndrome has remained an underdiagnosed condition. Awareness of presentation and prompt diagnostic workup are crucial for early identification and proper management. In this case report, we discuss a case of Primrose syndrome diagnosed in an infant born at Wellspan Hospital in York, PA. The patient exhibited classic phenotypic features, including a high hairline, high-arched palate, and brachycephaly at birth, as well as an absent corpus callosum observed on postnatal MRI and genotypic findings of a pathogenic variant in ZBTB20.
RESUMEN
The septins are filament-forming proteins found in diverse eukaryotes from fungi to vertebrates, with roles in cytokinesis, shaping of membranes and modifying cytoskeletal organization. These GTPases assemble into rod-shaped soluble hetero-hexamers and hetero-octamers in mammals, which polymerize into filaments and higher order structures. While the cell biology and pathobiology of septins are advancing rapidly, mechanistic study of the mammalian septins is limited by a lack of recombinant hetero-octamer materials. We describe here the production and characterization of a recombinant mammalian septin hetero-octamer of defined stoichiometry, the SEPT2/SEPT6/SEPT7/SEPT3 complex. Using a fluorescent protein fusion to the complex, we observed filaments assembled from this complex. In addition, we used this novel tool to resolve recent questions regarding the organization of the soluble septin complex. Biochemical characterization of a SEPT3 truncation that disrupts SEPT3-SEPT3 interactions is consistent with SEPT3 occupying a central position in the complex while the SEPT2 subunits are at the ends of the rod-shaped octameric complexes. Consistent with SEPT2 being on the complex ends, we find that our purified SEPT2/SEPT6/SEPT7/SEPT3 hetero-octamer copolymerizes into mixed filaments with separately purified SEPT2/SEPT6/SEPT7 hetero-hexamer. We expect this new recombinant production approach to lay essential groundwork for future studies into mammalian septin mechanism and function.