A CCR4-NOT Transcription Complex, Subunit 1, CNOT1, Variant Associated with Holoprosencephaly

Abstract

Holoprosencephaly is the incomplete separation of the forebrain during embryogenesis. Both genetic and environmental etiologies have been determined for holoprosencephaly; however, a genetic etiology is not found in most cases. In this report, we present two unrelated individuals with semilobar holoprosencephaly who have the identical de novo missense variant in the gene CCR4-NOT transcription complex, subunit 1 (CNOT1). The variant (c.1603C>T [p.Arg535Cys]) is predicted to be deleterious and is not present in public databases. CNOT1 has not been previously associated with holoprosencephaly or other brain malformations. In situ hybridization analyses of mouse embryos show that Cnot1 is expressed in the prosencephalic neural folds at gestational day 8.25 during the critical period for subsequent forebrain division. Combining human and mouse data, we show that CNOT1 is associated with incomplete forebrain division.

Keywords: CNOT1; holoprosencephaly; neonatal diabetes mellitus.

Figure 1

Patient Images (A) Proband 1 at age 12 months; facial characteristics include hypotelorism, epicanthal folds, depressed nasal bridge, and long philtrum. (B) Proband 1 at 15 months, note right ear microtia. Photo not available for proband 2.

Figure 2

CNOT1 Protein Domains CNOT1 c.1603C>T (p.Arg535Cys) (GenBank: NM_001265612.1) variant is located in the conserved HEAT domain

Figure 3

Gestational Day (GD) 8.25 Mouse Embryos A ventral view (top) is shown for whole mounts. Transverse sections (bottom) through the prosencephalic neural folds (at the level of the dashed line in schematic) were stained to visualize gene expression in specific cellular compartments. Abbreviations: nf, neural folds; h, heart; ne, neuroectoderm; hm, head mesenchyme; eem, extra-embryonic membranes. Scale bar = 100 μm.