Information on the health-related consequences of rare chromosome disorders is often limited, posing challenges for both patients and their families. The Chromosome 6 Project aims to bridge this knowledge gap for structural aberrations involving chromosome 6 by providing parents of affected children with information on the expected phenotypes of their child. To achieve this, detailed phenotype and genotype data are collected directly from parents worldwide and supplemented with data from literature reports, resulting thus far in a dataset of over 500 individuals. This comprehensive data pool was used to develop Del2Phen, a software tool introduced in this paper that generates aberration-specific phenotype information for chromosome disorders. Del2Phen identifies individuals with a deletion or duplication similar to that of a new patient (index) and produces a clinical description for the index based on phenotypic features observed in these genotypically similar individuals. Genotypic similarity is determined using existing knowledge on the haploinsufficiency effect of genes and established gene-phenotype relationships. The optimal genotypic similarity parameters for chromosome 6 deletions were evaluated, which led to thorough and reliable clinical descriptions based on sufficiently large groups of individuals with highly similar deletions. Although currently optimised for chromosome 6 deletions, Del2Phen can also be applied to deletions involving other chromosomes and is easily adapted for use on duplications, given sufficient data are available. Del2Phen can already be used to expedite data analysis for chromosome disorders, thus aiding healthcare professionals in delivering appropriate clinical care. Lastly, this tool will be integrated into an interactive website designed for parents of children with a chromosome 6 aberration, providing essential health information in a timely and accessible manner.

The scarcity of clinical information surrounding rare chromosome disorders poses challenges for parents and clinicians. To bridge this gap for chromosome 6 disorders, the Chromosome 6 Project collects detailed genotype and phenotype data, aiming to provide aberration-specific phenotype information to parents via an interactive website. With input from 32 parents and 21 professionals, including medical doctors, cytogeneticists, health psychologists, and communication specialists, we used a three-round Delphi method to determine the type and amount of health-related information to be presented on this website. A pre-Delphi questionnaire identified key factors for reporting clinical information online, forming the basis for 13 Delphi statements. Consensus was reached for 12 statements. Participants agreed that clinically relevant features should always be reported given their health impact, while parents also emphasized the importance of issues affecting the child's or family's well-being. Feature prevalence was supported as a guide for the order of reported features. To limit information overload, participants agreed on a reporting threshold for certain features. Finally, parents will be able to tailor the amount and type of information they view, with all details remaining accessible for future reference. While focused on chromosome 6 aberrations, these findings can inform the online information needs of families and professionals dealing with other rare genetic disorders.

Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart defect (CHD). TOF may present in isolation or in conjunction with one or more non-cardiac congenital anomalies or neurodevelopmental disorders (TOF+). Uncertainty regarding the efficacy of various genetic testing strategies, and an incomplete understanding of the genetic causes of TOF+, may lead to hesitancy in recommending genetic testing, particularly, clinical exome sequencing (cES). Here, we analyzed cES data from 131 individuals with TOF+. A definitive or probable diagnosis was made for 31 individuals, yielding a diagnostic rate of 23.6% (31/131). One individual received three diagnoses. Commercially available CHD panels would have detected only 27.3% (9/33) to 63.6% (21/33) of the diagnoses made by cES. We then used a machine learning approach to identify four genes for which there is sufficient evidence to support a phenotypic expansion including TOF: DVL3, MED13L, PUF60, and MEIS2. Since chromosomal microarray analysis (CMA) has been reported to have a diagnostic efficacy of 10-20% in individuals with TOF, we conclude that cES should be considered for all individuals with TOF+ for whom a molecular diagnosis has not been established by CMA. We also conclude that TOF represents a low penetrance phenotype associated with genetic syndromes caused by pathogenic variants in DVL3, MED13L, PUF60, and MEIS2.

Chromosome 6 aberrations, such as deletions and duplications (too little or too much chromosomal material, respectively), are extremely rare conditions with an estimated prevalence of less than 1 in 10,000 live births. Although chromosome aberrations can be diagnosed for more than 50 years, for most specific chromosome changes, still little is known about their effect on health and development. The lack of this knowledge is a burden for patients, parents and society. The Chromosome 6 Project aims to increase knowledge about rare chromosome 6 aberrations for both parents and professionals. The Chromosome 6 Project: Driven by parents, for parents is an ongoing collaboration with parents of an international Chromosome 6 Facebook group. It was on their initiative that the research started in 2013. The strength of the Chromosome 6 Project is involving parents, both in the setup of the study and in data collection directly from parents. We have shown that data reported by parents are reliable and useful for research purposes. This method of data collection has led to the largest complete database on chromosome 6 changes and to new knowledge on the clinical characteristics, development and behaviour of children with proximal 6q deletions (chromosome region 6q11q15), EPHA7 deletions (6q16.1), TAB2 deletions (6q25.1), terminal 6q26q27 deletions and terminal 6p25 deletions. The Chromosome 6 Project is an inspiring example of patient involvement in scientific research, for which recommendations are made by the researcher.

Terminal 6p deletions are rare, and information on their clinical consequences is scarce, which impedes optimal management and follow-up by clinicians. The parent-driven Chromosome 6 Project collaborates with families of affected children worldwide to better understand the clinical effects of chromosome 6 aberrations and to support clinical guidance. A microarray report is required for participation, and detailed phenotype information is collected directly from parents through a multilingual web-based questionnaire. Information collected from parents is then combined with case data from literature reports. Here, we present our findings on 13 newly identified patients and 46 literature cases with genotypically well-characterised terminal and subterminal 6p deletions. We provide phenotype descriptions for both the whole group and for subgroups based on deletion size and HI gene content. The total group shared a common phenotype characterised by ocular anterior segment dysgenesis, vision problems, brain malformations, congenital defects of the cardiac septa and valves, mild to moderate hearing impairment, eye movement abnormalities, hypotonia, mild developmental delay and dysmorphic features. These characteristics were observed in all subgroups where FOXC1 was included in the deletion, confirming a dominant role for this gene. Additional characteristics were seen in individuals with terminal deletions exceeding 4.02 Mb, namely complex heart defects, corpus callosum abnormalities, kidney abnormalities and orofacial clefting. Some of these additional features may be related to the loss of other genes in the terminal 6p region, such as RREB1 for the cardiac phenotypes and TUBB2A and TUBB2B for the cerebral phenotypes. In the newly identified patients, we observed previously unreported features including gastrointestinal problems, neurological abnormalities, balance problems and sleep disturbances. We present an overview of the phenotypic characteristics observed in terminal and subterminal 6p deletions. This reveals a common phenotype that can be highly attributable to haploinsufficiency of FOXC1, with a possible additional effect of other genes in the 6p25 region. We also delineate the developmental abilities of affected individuals and report on previously unrecognised features, showing the added benefit of collecting information directly from parents. Based on our overview, we provide recommendations for clinical surveillance to support clinicians, patients and families.

Background Even with the introduction of new genetic techniques that enable accurate genomic characterization, knowledge about the phenotypic spectrum of rare chromosomal disorders is still limited, both in literature and existing databases. Yet this clinical information is of utmost importance for health professionals and the parents of children with rare diseases. Since existing databases are often hampered by the limited time and willingness of health professionals to input new data, we collected phenotype data directly from parents of children with a chromosome 6 disorder. These parents were reached via social media, and the information was collected via the online Chromosome 6 Questionnaire, which includes 115 main questions on congenital abnormalities, medical problems, behaviour, growth and development. Methods Here, we assess data consistency by comparing parent-reported phenotypes to phenotypes based on copies of medical files for the same individual (n = 20) and data availability by comparing the data available on specific characteristics reported by parents (n = 34) to data available in existing literature (n = 39). Results The reported answers to the main questions on phenotype characteristics were 85–95% consistent, and the consistency of answers to subsequent more detailed questions was 77–96%. For all but two main questions, significantly more data was collected from parents via the Chromosome 6 Questionnaire than was currently available in literature. For the topics developmental delay and brain abnormalities, no significant difference in the amount of available data was found. The only feature for which significantly more data was available in literature was a sub-question on the type of brain abnormality present. Conclusion This is the first study to compare phenotype data collected directly from parents to data extracted from medical files on the same individuals. We found that the data was highly consistent, and phenotype data collected via the online Chromosome 6 Questionnaire resulted in more available information on most clinical characteristics when compared to phenotypes reported in literature reports thus far. We encourage active patient participation in rare disease research and have shown that parent-reported phenotypes are reliable and contribute to our knowledge of the phenotypic spectrum of rare chromosomal disorders.

Background Terminal 6q deletions are rare, and the number of well-defined published cases is limited. Since parents of children with these aberrations often search the internet and unite via international social media platforms, these dedicated platforms may hold valuable knowledge about additional cases. The Chromosome 6 Project is a collaboration between researchers and clinicians at the University Medical Center Groningen and members of a Chromosome 6 support group on Facebook. The aim of the project is to improve the surveillance of patients with chromosome 6 aberrations and the support for their families by increasing the available information about these rare aberrations. This parent-driven research project makes use of information collected directly from parents via a multilingual online questionnaire. Here, we report our findings on 93 individuals with terminal 6q deletions and 11 individuals with interstitial 6q26q27 deletions, a cohort that includes 38 newly identified individuals. Results Using this cohort, we can identify a common terminal 6q deletion phenotype that includes microcephaly, dysplastic outer ears, hypertelorism, vision problems, abnormal eye movements, dental abnormalities, feeding problems, recurrent infections, respiratory problems, spinal cord abnormalities, abnormal vertebrae, scoliosis, joint hypermobility, brain abnormalities (ventriculomegaly/hydrocephaly, corpus callosum abnormality and cortical dysplasia), seizures, hypotonia, ataxia, torticollis, balance problems, developmental delay, sleeping problems and hyperactivity. Other frequently reported clinical characteristics are congenital heart defects, kidney problems, abnormalities of the female genitalia, spina bifida, anal abnormalities, positional foot deformities, hypertonia and self-harming behaviour. The phenotypes were comparable up to a deletion size of 7.1 Mb, and most features could be attributed to the terminally located gene DLL1 . Larger deletions that include QKI (>7.1 Mb) lead to a more severe phenotype that includes additional clinical characteristics. Conclusions Terminal 6q deletions cause a common but highly variable phenotype. Most clinical characteristics can be linked to the smallest terminal 6q deletions that include the gene DLL1 (>500 kb). Based on our findings, we provide recommendations for clinical follow-up and surveillance of individuals with terminal 6q deletions.

Deletions that include the gene TAB2 and TAB2 loss-of-function variants have previously been associated with congenital heart defects and cardiomyopathy. However, other features, including short stature, facial dysmorphisms, connective tissue abnormalities and a variable degree of developmental delay, have only been mentioned occasionally in literature and thus far not linked to TAB2 . In a large-scale, social media-based chromosome 6 study, we observed a shared phenotype in patients with a 6q25.1 deletion that includes TAB2 . To confirm if this phenotype is caused by haploinsufficiency of TAB2 and to delineate a TAB2 -related phenotype, we subsequently sequenced TAB2 in patients with matching phenotypes and recruited patients with pathogenic TAB2 variants detected by exome sequencing. This identified 11 patients with a deletion containing TAB2 (size 1.68–14.31 Mb) and 14 patients from six families with novel truncating TAB2 variants. Twenty (80%) patients had cardiac disease, often mitral valve defects and/or cardiomyopathy, 18 (72%) had short stature and 18 (72%) had hypermobility. Twenty patients (80%) had facial features suggestive for Noonan syndrome. No substantial phenotypic differences were noted between patients with deletions and those with intragenic variants. We then compared our patients to 45 patients from the literature. All literature patients had cardiac diseases, but syndromic features were reported infrequently. Our study shows that the phenotype in 6q25.1 deletions is caused by haploinsufficiency of TAB2 and that TAB2 is associated not just with cardiac disease, but also with a distinct phenotype, with features overlapping with Noonan syndrome. We propose the name “ TAB2 -related syndrome”.

Ephrin receptor and their ligands, the ephrins, are widely expressed in the developing brain. They are implicated in several developmental processes that are crucial for brain development. Deletions in genes encoding for members of the Eph/ephrin receptor family were reported in several neurodevelopmental disorders. The ephrin receptor A7 gene (EPHA7) encodes a member of ephrin receptor subfamily of the protein-tyrosine kinase family. EPHA7 plays a role in corticogenesis processes, determines brain size and shape, and is involved in development of the central nervous system. One patient only was reported so far with a de novo deletion encompassing EPHA7 in 6q16.1. We report 12 additional patients from nine unrelated pedigrees with similar deletions. The deletions were inherited in nine out of 12 patients, suggesting variable expressivity and incomplete penetrance. Four patients had tiny deletions involving only EPHA7, suggesting a critical role of EPHA7 in a neurodevelopmental disability phenotype. We provide further evidence for EPHA7 deletion as a risk factor for neurodevelopmental disorder and delineate its clinical phenotype.

Proximal 6q (6q11-q15) deletions are extremely rare and little is known about their phenotypic consequences. Since parents and caregivers now use social media to seek information on rare disorders, the Chromosome 6 Project has successfully collaborated with a Facebook group to collect data on individuals worldwide. Here we describe a cohort of 20 newly identified individuals and 25 literature cases with a proximal 6q deletion. Microarray results and phenotype data were reported directly by parents via a multilingual online questionnaire. This led to phenotype descriptions for five subregions of proximal 6q deletions; comparing the subgroups revealed that 6q11q14.1 deletions presented less severe clinical characteristics than 6q14.2q15 deletions. Gastroesophageal reflux, tracheo/laryngo/bronchomalacia, congenital heart defects, cerebral defects, seizures, and vision and respiratory problems were predominant in those with 6q14.2q15 deletions. Problems related to connective tissue (hypermobility, hernias and foot deformities) were predominantly seen in deletions including the COL12A1 gene (6q13). Congenital heart defects could be linked to deletions of MAP3K7 (6q15) or TBX18 (6q14.3). We further discuss the role of ten genes known or assumed to be related to developmental delay and/or autism (BAI3, RIMS1, KCNQ5, HTR1B, PHIP, SYNCRIP, HTR1E, ZNF292, AKIRIN2 and EPHA7). The most influential gene on the neurodevelopmental phenotype seems to be SYNCRIP (6q14.3), while deletions that include more than two of these genes led to more severe developmental delay. We demonstrate that approaching individuals via social media and collecting data directly from parents is a successful strategy, resulting in better information to counsel families.