Chin-To Fong

Recurrent reciprocal 1q21.1 deletions and duplications associated with microcephaly or macrocephaly and developmental and behavioral abnormalities

Chromosome region 1q21.1 contains extensive and complex low-copy repeats, and copy number variants (CNVs) in this region have recently been reported in association with congenital heart defects, developmental delay, schizophrenia and related psychoses. We describe 21 probands with the 1q21.1 microdeletion and 15 probands with the 1q21.1 microduplication. These CNVs were inherited in most of the cases in which parental studies were available. Consistent and statistically significant features of microcephaly and macrocephaly were found in individuals with microdeletion and microduplication, respectively. Notably, a paralog of the HYDIN gene located on 16q22.2 and implicated in autosomal recessive hydrocephalus was inserted into the 1q21.1 region during the evolution of Homo sapiens; we found this locus to be deleted or duplicated in the individuals we studied, making it a probable candidate for the head size abnormalities observed. We propose that recurrent reciprocal microdeletions and microduplications within 1q21.1 represent previously unknown genomic disorders characterized by abnormal head size along with a spectrum of developmental delay, neuropsychiatric abnormalities, dysmorphic features and congenital anomalies. These phenotypes are subject to incomplete penetrance and variable expressivity.

Hermansky-Pudlak syndrome is caused by mutations in HPS4, the human homolog of the mouse light-ear gene.

Hermansky-Pudlak syndrome (HPS) is a disorder of organelle biogenesis in which oculocutaneous albinism, bleeding and pulmonary fibrosis result from defects of melanosomes, platelet dense granules and lysosomes. HPS is common in Puerto Rico, where it is caused by mutations in the genes HPS1 and, less often, HPS3 (ref. 8). In contrast, only half of non–Puerto Rican individuals with HPS have mutations in HPS1 (ref. 9), and very few in HPS3 (ref. 10). In the mouse, more than 15 loci manifest mutant phenotypes similar to human HPS, including pale ear (ep), the mouse homolog of HPS1 (refs 13,14). Mouse ep has a phenotype identical to another mutant, light ear (le), which suggests that the human homolog of le is a possible human HPS locus. We have identified and found mutations of the human le homolog, HPS4, in a number of non–Puerto Rican individuals with HPS, establishing HPS4 as an important HPS locus in humans. In addition to their identical phenotypes, le and ep mutant mice have identical abnormalities of melanosomes, and in transfected melanoma cells the HPS4 and HPS1 proteins partially co-localize in vesicles of the cell body. In addition, the HPS1 protein is absent in tissues of le mutant mice. These results suggest that the HPS4 and HPS1 proteins may function in the same pathway of organelle biogenesis.

Microdeletions including YWHAE in the Miller-Dieker syndrome region on chromosome 17p13.3 result in facial dysmorphisms, growth restriction, and cognitive impairment

Background: Deletions in the 17p13.3 region are associated with abnormal neuronal migration. Point mutations or deletion copy number variants of the PAFAH1B1 gene in this genomic region cause lissencephaly, whereas extended deletions involving both PAFAH1B1 and YWHAE result in Miller–Dieker syndrome characterised by facial dysmorphisms and a more severe grade of lissencephaly. The phenotypic consequences of YWHAE deletion without deletion of PAFAH1B1 have not been studied systematically. Methods: We performed a detailed clinical and molecular characterization of five patients with deletions involving YWHAE but not PAFAH1B1, two with deletion including PAFAH1B1 but not YWHAE, and one with deletion of YWHAE and mosaic for deletion of PAFAH1B1. Results: Three deletions were terminal whereas five were interstitial. Patients with deletions including YWHAE but not PAFAH1B1 presented with significant growth restriction, cognitive impairment, shared craniofacial features, and variable structural abnormalities of the brain. Growth restriction was not observed in one patient with deletion of YWHAE and TUSC5, implying that other genes in the region may have a role in regulation of growth with CRK being the most likely candidate. Using array based comparative genomic hybridisation and long range polymerase chain reaction, we have delineated the breakpoints of these nonrecurrent deletions and show that the interstitial genomic rearrangements are likely generated by diverse mechanisms, including the recently described Fork Stalling and Template Switching (FoSTeS)/Microhomology Mediated Break Induced Replication (MMBIR). Conclusions: Microdeletions of chromosome 17p13.3 involving YWHAE present with growth restriction, craniofacial dysmorphisms, structural abnormalities of brain and cognitive impairment. The interstitial deletions are mediated by diverse molecular mechanisms.

Parameters of Care for Craniosynostosis

Background A multidisciplinary meeting was held from March 4 to 6, 2010, in Atlanta, Georgia, entitled “Craniosynostosis: Developing Parameters for Diagnosis, Treatment, and Management.” The goal of this meeting was to create parameters of care for individuals with craniosynostosis. Methods Fifty-two conference attendees represented a broad range of expertise, including anesthesiology, craniofacial surgery, dentistry, genetics, hand surgery, neurosurgery, nursing, ophthalmology, oral and maxillofacial surgery, orthodontics, otolaryngology, pediatrics, psychology, public health, radiology, and speech-language pathology. These attendees also represented 16 professional societies and peer-reviewed journals. The current state of knowledge related to each discipline was reviewed. Based on areas of expertise, four breakout groups were created to reach a consensus and draft specialty-specific parameters of care based on the literature or, in the absence of literature, broad clinical experience. In an iterative manner, the specialty-specific draft recommendations were presented to all conference attendees. Participants discussed the recommendations in multidisciplinary groups to facilitate exchange and consensus across disciplines. After the conference, a pediatric intensivist and social worker reviewed the recommendations. Results Consensus was reached among the 52 conference attendees and two post hoc reviewers. Longitudinal parameters of care were developed for the diagnosis, treatment, and management of craniosynostosis in each of the 18 specialty areas of care from prenatal evaluation to adulthood. Conclusions To our knowledge, this is the first multidisciplinary effort to develop parameters of care for craniosynostosis. These parameters were designed to help facilitate the development of educational programs for the patient, families, and health-care professionals; stimulate the creation of a national database and registry to promote research, especially in the area of outcome studies; improve credentialing of interdisciplinary craniofacial clinical teams; and improve the availability of health insurance coverage for all individuals with craniosynostosis.

X-linked female band heterotopia-male lissencephaly syndrome

We report a family with band heterotopia in a mother and daughter and lissencephaly in a son (X-linked inheritance pattern). Postmortem examination of the boy revealed classical lissencephaly and, among other findings, simplified and discontinuous inferior olives without inferior olivary heterotopia. The absence of inferior olivary heterotopia may distinguish X-linked lissencephaly from other conditions with classic lissencephaly such as Miller-Dieker syndrome.

Mutations in PURA Cause Profound Neonatal Hypotonia, Seizures, and Encephalopathy in 5q31.3 Microdeletion Syndrome

5q31.3 microdeletion syndrome is characterized by neonatal hypotonia, encephalopathy with or without epilepsy, and severe developmental delay, and the minimal critical deletion interval harbors three genes. We describe 11 individuals with clinical features of 5q31.3 microdeletion syndrome and de novo mutations in PURA, encoding transcriptional activator protein Pur-α, within the critical region. These data implicate causative PURA mutations responsible for the severe neurological phenotypes observed in this syndrome.

Duplications of the critical Rubinstein–Taybi deletion region on chromosome 16p13.3 cause a novel recognisable syndrome

Background The introduction of molecular karyotyping technologies facilitated the identification of specific genetic disorders associated with imbalances of certain genomic regions. A detailed phenotypic delineation of interstitial 16p13.3 duplications is hampered by the scarcity of such patients. Objectives To delineate the phenotypic spectrum associated with interstitial 16p13.3 duplications, and perform a genotype-phenotype analysis. Results The present report describes the genotypic and phenotypic delineation of nine submicroscopic interstitial 16p13.3 duplications. The critically duplicated region encompasses a single gene, CREBBP, which is mutated or deleted in Rubinstein–Taybi syndrome. In 10 out of the 12 hitherto described probands, the duplication arose de novo. Conclusions Interstitial 16p13.3 duplications have a recognizable phenotype, characterized by normal to moderately retarded mental development, normal growth, mild arthrogryposis, frequently small and proximally implanted thumbs and characteristic facial features. Occasionally, developmental defects of the heart, genitalia, palate or the eyes are observed. The frequent de novo occurrence of 16p13.3 duplications demonstrates the reduced reproductive fitness associated with this genotype. Inheritance of the duplication from a clinically normal parent in two cases indicates that the associated phenotype is incompletely penetrant.

A Yeast Artificial Chromosome Contig Encompassing the Type 1 Neurofibromatosis Gene

The yeast artificial chromosome (YAC) system (Burke et al., 1987, Science 236: 806-812) allows the direct cloning of large regions of the genome. A YAC contig map of approximately 700 kb encompassing the region surrounding the type 1 neurofibromatosis (NF1) locus on 17q11.2 has been constructed. A single YAC containing the entire NF1 locus has been constructed by homologous recombination in yeast. In the process of contig construction a novel method of YAC end rescue has been developed by YAC circularization in yeast and plasmid rescue in bacteria. YACs containing homology to the NF1 region but mapping to another chromosome have also been discovered. Sequences of portions of the homologous locus indicate that this other locus is a nonprocessed pseudogene.

Suppression of tumorigenicity in human ovarian carcinoma cell line SKOV-3 by microcell-mediated transfer of chromosome 11

To determine the pathogenic role of chromosomes 11 and 17 in the carcinogenesis of human ovarian cancers, neo(R)-tagged chromosome 11 or 17 was transferred from cell lines A9H11 or A9H17, respectively, into the ovarian carcinoma cell line SKOV-3 using microcell-mediated chromosome transfer. The chromosome transfer was verified by polymerase chain reaction detection of the neo(R) gene, fluorescence in situ hybridization detection of an extra chromosome 11, and microsatellite polymorphism detection of an exogeneous chromosome 11. Five SKOV-3/A9H11 hybrids and five SKOV-3/A9H17 hybrid clones were generated. For the chromosome 11 transfer, complete suppression of tumorigenicity was observed in four clones, (11)9-8 and 11(H)7-2, 11(H)8-3, and 11(H)7-2, 100 days post implantation. For the chromosome 17 transfer, no complete suppression of tumorigenicity was observed. However, an increased latency period ranging from 25 to 49 days in contrast to 7 days for the SKOV-3 parental line, and a significant reduction in tumor size was observed. There was no correlation between the in vitro growth rate and the tumorigenicity or length of latency period. Our results demonstrate functionally that chromosome 11 may carry a tumor suppressor gene(s) while chromosome 17 may carry a tumor growth-inhibitor gene(s) for the ovarian carcinoma cell line, SKOV-3.

Association of nasomaxillary asymmetry in children with unilateral cleft lip and palate and their parents

OBJECTIVE It has been suggested previously that increased width of midfacial structures is associated with the development of palatal clefting. The aim of this study was to evaluate the association of transverse craniofacial asymmetry between children with unilateral cleft lip and palate (UCLP) and their parents. Specifically, we hypothesized that parental transverse craniofacial asymmetry is a risk factor associated with the development of asymmetry in children with UCLP. DESIGN Retrospective cross-sectional investigation including affected children and their noncleft parents. PATIENTS, PARTICIPANTS A total of 64 children-parent sets of data (32 child-biological mother + 32 child-biological father) were included. Subject records included posteroanterior cephalometric radiographs obtained from 29 Costa Rican families with UCLP. MAIN OUTCOME MEASURES The side of parental nasal asymmetry was significantly associated with the side of cleft in their children. For the majority of parents with children suffering from a left cleft, nasal width was larger on the left, compared with the right side. Similarly, in the majority of parents with children suffering from a right cleft, nasal width was larger on the right, compared with the left side. CONCLUSION The results suggest that unilaterally increased nasomaxillary width in parents may play a key role in the development of ipsilateral palatal clefting in their offspring, therefore underscoring the importance of craniofacial form as a genetic etiologic factor in the genesis of clefting. Better understanding of the role of craniofacial form in cleft development will ultimately allow for the assessment of risk for cleft lip and palate.