A Mouse Splice-Site Mutant and Individuals with Atypical Chromosome 22q11.2 Deletions Demonstrate the Crucial Role for Crkl in Craniofacial and Pharyngeal Development

Abstract

The 22q11.2 deletion syndrome (22q11DS) is thought to be a contiguous gene syndrome caused by haploinsufficiency for a variable number of genes with overlapping function during the development of the craniofacial, pharyngeal and cardiac structures. The complexity of genetic and developmental anomalies resulting in 22q11DS has made attributing causation to specific genes difficult. The CRKL gene resides within the common 3-Mb region, most frequently affected in 22q11DS, and has been shown to play an essential role in the development of tissues affected in 22q11DS. Here, we report the characterisation of a mouse strain we named ‘snoopy', harbouring a novel Crkl splice-site mutation that results in a loss of Crkl expression. The snoopy strain exhibits a variable phenotype that includes micrognathia, pharyngeal occlusion, aglossia and holoprosencephaly, and altered retinoic acid and endothelin signalling. Together, these features are reminiscent of malformations occurring in auriculocondylar syndrome and agnathia-otocephaly complex, 2 conditions not previously associated with the CRKL function. Comparison of the features of a cohort of patients harbouring small 22q11.2 deletions centred over the CRKL gene, but sparing TBX1, highlights the role of CRKL in contributing to the craniofacial features of 22q11DS. These analyses demonstrate the central role of Crkl in regulating signalling events in the developing oropharyngeal complex and its potential to contribute to dysmorphology.

SNP microarray abnormalities in a cohort of 28 infants with congenital diaphragmatic hernia

“…There are a number of patients described in the literature with deletions of this region demonstrating cardiac defects and mild dysmorphism [Kurahashi et al, ; Garcia‐Minaur et al, ; Rauch et al, ; Fernandez et al, ; Yu et al, ; Verhagen et al, ; Zhao et al, ; Racedo et al, ]. In addition, mice with crkl mutations manifest defects of neural crest derivatives including aortic arch arteries, cardiac outflow tract, thymus, parathyroid glands and craniofacial structures [Guris et al, ; Miller et al, ; Racedo et al, ], highlighting a developmental role of CRKL.…”

In the line-up: deleted genes associated with DiGeorge/22q11.2 deletion syndrome: are they all suspects?

“…Crkl is expressed at high levels in pharyngeal arches, neural crest, and brain, and homozygous deletion compromises neural crest derivatives including cranial ganglia, aortic arch arteries, thymus, parathyroid glands, and craniofacial structures, leading to late-gestation lethality [70]. Homozygous loss-of-function in Snoopy , a point Crkl mutation [71], also results in craniofacial anomalies, pharyngeal occlusion, and holoprosencephaly. Snoopy or Crkl +/− : Tbx1 +/− compound heterozygotes ( Tbx1 , an A to B gene, see below) have increased retinoic acid (RA) signaling, also seen in mouse embryos with an A to B deletion ( LgDel ) [71–74] .…”

“…Homozygous loss-of-function in Snoopy , a point Crkl mutation [71], also results in craniofacial anomalies, pharyngeal occlusion, and holoprosencephaly. Snoopy or Crkl +/− : Tbx1 +/− compound heterozygotes ( Tbx1 , an A to B gene, see below) have increased retinoic acid (RA) signaling, also seen in mouse embryos with an A to B deletion ( LgDel ) [71–74] . Crkl may interact with other inductive signaling pathways; fibroblast growth factor (FGF) receptors directly bind to the Ckrl SH2 domain [75].…”

Oculo-auriculo-vertebral spectrum: Clinical and molecular analysis of 51 patients

“…In fact, an altered retinoic acid and endothelin signaling has been an evidenced in a Crkl mutant mouse. These two signaling pathways play an important role in the migrating and differentiation of neural crest cells in the branchial arches during embryogenesis [52].…”