Cecr2 mutant mice as a model for human cat eye syndrome

Cat eye syndrome (CES), a human genetic disorder caused by the inverted duplication of a region on chromosome 22, has been known since the late 1890s. Despite the significant impact this disorder has on affected individuals, models for CES have not been produced due to the difficulty of effectively duplicating the corresponding chromosome region in an animal model. However, the study of phenotypes associated with individual genes in this region such as CECR2 may shed light on the etiology of CES. In this study we have shown that deleterious loss of function mutations in mouse Cecr2 effectively demonstrate many of the abnormal features present in human patients with CES, including coloboma and specific skeletal, kidney and heart defects. Beyond phenotypic analyses we have demonstrated the importance of utilizing multiple genetic backgrounds to study disease models, as we see major differences in penetrance of Cecr2-related abnormal phenotype between mouse strains, reminiscent of the variability in the human syndrome. These findings suggest that Cecr2 is involved in the abnormal features of CES and that Cecr2 mice can be used as a model system to study the wide range of phenotypes present in CES.

Rapid adaptation to human protein kinase R by a unique genomic rearrangement in rhesus cytomegalovirus

Cytomegaloviruses (CMVs) are generally unable to cross species barriers, in part because prolonged coevolution with one host species limits their ability to evade restriction factors in other species. However, the limitation in host range is incomplete. For example, rhesus CMV (RhCMV) can replicate in human cells, albeit much less efficiently than in rhesus cells. Previously we reported that the protein kinase R (PKR) antagonist encoded by RhCMV, rTRS1, has limited activity against human PKR but is nonetheless necessary and sufficient to enable RhCMV replication in human fibroblasts (HF). We now show that knockout of PKR in human cells or treatment with the eIF2B agonist ISRIB, which overcomes the translational inhibition resulting from PKR activation, augments RhCMV replication in HF, indicating that human PKR contributes to the inefficiency of RhCMV replication in HF. Serial passage of RhCMV in HF reproducibly selected for viruses with improved ability to replicate in human cells. The evolved viruses contain an inverted duplication of the terminal 6.8 kb of the genome, including rTRS1. The duplication replaces ~11.8 kb just downstream of an internal sequence element, pac1-like, which is very similar to the pac1 cleavage and packaging signal found near the terminus of the genome. Plaque-purified evolved viruses produced at least twice as much rTRS1 as the parental RhCMV and blocked the PKR pathway more effectively in HF. Southern blots revealed that unlike the parental RhCMV, viruses with the inverted duplication isomerize in a manner similar to HCMV and other herpesviruses that have internal repeat sequences. The apparent ease with which this duplication event occurs raises the possibility that the pac1-like site, which is conserved in Old World monkey CMV genomes, may serve a function in facilitating rapid adaptation to evolutionary obstacles.

Rapid adaptation to human protein kinase R by a unique genomic rearrangement in rhesus cytomegalovirus

ABSTRACTCytomegaloviruses (CMVs) are generally unable to cross species barriers, in part because prolonged coevolution with one host species limits their ability to evade restriction factors in other species. However, the limitation in host range is incomplete. For example, rhesus CMV (RhCMV) can replicate in human cells, albeit much less efficiently than in rhesus cells. Previously we reported that the protein kinase R (PKR) antagonist encoded by RhCMV, rTRS1, has limited activity against human PKR but is nonetheless necessary and sufficient to enable RhCMV replication in human fibroblasts (HF). We now show that knockout of PKR in human cells or treatment with the eIF2B agonist ISRIB, which overcomes the translational inhibition resulting from PKR activation, augments RhCMV replication in HF, indicating that human PKR contributes to the inefficiency of RhCMV replication in HF. Serial passage of RhCMV in HF reproducibly selected for viruses with improved fitness in human cells. The evolved viruses contain an inverted duplication of the terminal 6.8 kb of the genome, including rTRS1. The duplication replaces ~11.8 kb just downstream of an internal sequence element, pac1-like, which is very similar to the pac1 cleavage and packaging signal found near the terminus of the genome. Plaque-purified evolved viruses produced at least twice as much rTRS1 as the parental RhCMV and blocked the PKR pathway more effectively in HF. Southern blots revealed that unlike the parental RhCMV, viruses with the inverted duplication isomerize in a manner similar to HCMV and other herpesviruses that have internal repeat sequences. The apparent ease with which this duplication event occurs raises the possibility that the pac1-like site, which is conserved in Old World monkey CMV genomes, may serve a function in facilitating rapid adaptation to evolutionary obstacles.AUTHOR SUMMARYRhesus macaque CMV (RhCMV) is an important model for human CMV (HCMV) pathogenesis and vaccine development. Therefore, it is important to understand the similarities and differences in infectivity and interaction of these viruses with their host species. In contrast to the strict species-specificity of HCMV, RhCMV is able to cross species barriers to replicate in human cells. We know from past work that a component of this broader host range is RhCMV’s ability to counteract both the rhesus and human versions of a key antiviral factor. Here we delve further into the mechanisms by which RhCMV can adapt to counteract human cellular defenses. We find that RhCMV appears to be poised to undergo a specific genomic rearrangement that facilitates increased replication efficiency in human cells. Besides providing insights into CMV species-specificity and host barriers to cross-species transmission, this work also provides more generalized clues about viral adaptative mechanisms.

A clinical case of inverted duplication with terminal deletion of the short arm of chromosome 5

The 5p inverted duplication deletion syndrome, also known as inv dup del 5p, is a rare genetic disorder with a prevalence of below 1:1 000 000, whose underlying abnormality lies in a segmental trisomy and simultaneous segmental monosomy of the short arm of chromosome 5. The syndrome was first described by A. Kleczkowska et al. in 1987. According to the literature, large duplications of the chromosome 5 short arm are associated with pronounced phenotypic manifestations, delayed speech and mental development, as well as congenital cardiac, brain and musculoskeletal malformations. We present a description of a clinical case of extended inverted duplication with deletion of the chromosome 5 short arm in a girl with a mild phenotype and no visceral or musculoskeletal abnormalities; we also discuss the pathogenetic mechanisms of chromosomal rearrangement, and conduct a comparative analysis of phenotypic manifestations based on the available literature. Comprehensive molecular cytogenetic assessments have demonstrated that the duplicated site has a length of 29 Mb (5p13.3p15.33), and the deleted site of the subtelomeric region distal to 5p15.33 has a length of 110 kb.

Deciphering the Invdupdel(8p) Genotype–Phenotype Correlation: Our Opinion

The 8p inverted duplication/deletion is a rare chromosomal rearrangement clinically featuring neurodevelopmental delay, mild to severe cognitive impairment, heart congenital defects and brain abnormalities. Patients affected also present typical facial dysmorphisms and skeletal malformations, and it is thought that the composite clinical picture may fall into the chromosomal rearrangement architecture. With the major aim of better framing its related clinical and diagnostic paths, we describe a patient carrying a de novo invdupde[8p] whose clinical features have not been described so far. Hence, through an extensive genotype–phenotype correlation analysis and by reviewing the dedicated scientific literature, we compared our patient’s features with those reported in other patients, which allows us to place our proband’s expressiveness in an intermediate area, widening the scope of the already known invdupde[8p] genotype–phenotype relationship.