Directly Transmitted 12.3-Mb Deletion with a Consistent Phenotype in the Variable 11q21q22.3 Region

A mutational hotspot in AMOTL1 defines a new syndrome of orofacial clefting, cardiac anomalies, and tall stature

AMOTL1 encodes angiomotin-like protein 1, an actin-binding protein that regulates cell polarity, adhesion, and migration. The role of AMOTL1 in human disease is equivocal. We report a large cohort of individuals harboring heterozygous AMOTL1 variants and define a core phenotype of orofacial clefting, congenital heart disease, tall stature, auricular anomalies, and gastrointestinal manifestations in individuals with variants in AMOTL1 affecting amino acids 157-161, a functionally undefined but highly conserved region. Three individuals with AMOTL1 variants outside this region are also described who had variable presentations with orofacial clefting and multi-organ disease. Our case cohort suggests that heterozygous missense variants in AMOTL1, most commonly affecting amino acid residues 157-161, define a new orofacial clefting syndrome, and indicates an important functional role for this undefined region.

De novo interstitial deletion of 11q14.3q22 in a boy with mild intellectual disability and short stature

BACKGROUND

Interstitial deletions of the 11q region are infrequent. Nonrecurrent chromosomal rearrangements are observed with high variability in size and precise breakpoints of the deleted area. Moreover  heterogeneous clinical findings are observed in those harboring 11q interstitial deletions. Main clinical features associated with these deletions include mild dysmorphic findings  intellectual disability and moderate developmental or speech delay .

METHOD

Conventional high-resolution karyotyping along with microarray studies were performed for the index patient  who was found to be a carrier of a de novo interstitial deletion in the long arm of chromosome 11  which is located between the 11q14 and 11q22 band regions. We also investigated the homologous chromosome with next-generation sequencing technology to search for unmasked recessive variants in genes on the nondeleted contralateral allele.

RESULTS

Cytogenetic analysis revealed a de novo interstitial deletion on the long arm of chromosome 11  46 XY del(11) (q14q22). Microarray analysis confirmed the deletion of 11.2 Mb in length  mapping from 11q14.3 to 11q22.2 [arr (GRCh37) 11q14.3q22.1(90549863_101833022)x1 dn]. Whole-exome sequencing did not detect any other genetic variant (single nucleotide variant ) on the nondeleted allele.

CONCLUSION

This study gave us the opportunity for an attempt to define the smallest region of overlap for frequently observed clinical findings by reviewing the literature.

A Central Role of Telomere Dysfunction in the Formation of a Unique Translocation within the Sub-Telomere Region Resulting in Duplication and Partial Trisomy

Telomeres play a major role in maintaining genome stability and integrity. Putative involvement of telomere dysfunction in the formation of various types of chromosomal aberrations is an area of active research. Here, we report a case of a six-month-old boy with a chromosomal gain encompassing the 11q22.3q25 region identified by SNP array analysis. The size of the duplication is 26.7 Mb and contains 170 genes (OMIM). The duplication results in partial trisomy of the region in question with clinical consequences, including bilateral renal dysplasia, delayed development, and a heart defect. Moreover, the karyotype determined by R-banding and chromosome painting as well as by hybridization with specific sub-telomere probes revealed the presence of an unbalanced t(9;11)(p24;q22.3) translocation with a unique breakpoint involving the sub-telomere region of the short arm of chromosome 9. The karyotypes of the parents were normal. Telomere integrity in circulating lymphocytes from the child and from his parents was assessed using an automated high-throughput method based on fluorescence in situ hybridization (FISH) with telomere- and centromere-specific PNA probes followed by M-FISH multicolor karyotyping. Very short telomeres, as well as an increased frequency of telomere loss and formation of telomere doublets, were detected in the child’s cells. Interestingly, similar telomere profiles were found in the circulating lymphocytes of the father. Moreover, an assessment of clonal telomere aberrations identified chromosomes 9 and 11 with particularly high frequencies of such aberrations. These findings strongly suggest that telomere dysfunction plays a central role in the formation of this specific unbalanced chromosome rearrangement via chromosome end-to-end fusion and breakage–fusion–bridge cycles.