Impacts of variants of uncertain significance on parental perceptions of children after prenatal chromosome microarray testing

Perinatal outcomes and genomic characteristics of fetal copy number variants: An individual record linkage study of 713 pregnancies

OBJECTIVE

To determine the perinatal outcomes of fetuses diagnosed with a pathogenic copy number variant (CNV) or variant of uncertain significance (VUS); and to characterize these variants in terms of testing indication, genomic location, size, and inheritance.

METHODS

Retrospective study of singleton pregnancies with a pathogenic CNV or VUS from a single laboratory during 2012-2018. Probabilistic record linkage between the prenatal diagnosis dataset and perinatal outcome data for births from 20 weeks gestation was performed. If no birth record was found, this implied a pregnancy loss <20 weeks.

RESULTS

We included 6945 prenatal microarray results; a pathogenic CNV was detected in 230 (3.3%, 95% CI: 2.9%-3.8%) and a VUS in 483 (7.0%, 95% CI: 6.4%-7.6%). Of pregnancies with a pathogenic CNV, 20.0% (95% CI: 15.3%-25.6%) had a live birth, 3.0% (95% CI: 1.5%-6.2%) had a perinatal death (stillbirth or neonatal death), and 77% (95% CI: 71.1%-81.9%) had no birth record. Of those with a VUS, 64.4% (95% CI: 60.0%-68.5%) had a live birth, 1.8% (95% CI: 1.0%-3.5%) had a perinatal death, and no birth record was found for 33.7% (95% CI: 29.7%-38.1%). Most pathogenic CNVs (61.1%) were <7 Mb in size. The most common microdeletion syndromes were DiGeorge, Wolf-Hirschhorn, and Cri-du-chat syndromes.

CONCLUSION

This study provides an overview of perinatal outcomes and frequency of recurrent CNVs observed in the prenatal microarray era.

Information is power: The experiences, attitudes and needs of individuals who chose to have prenatal genomic sequencing for fetal anomalies

OBJECTIVE

This study sought to evaluate the experiences of individuals who chose to participate in a study and receive prenatal genomic sequencing (pGS) for fetuses with congenital structural anomalies.

METHOD

Individuals who received research results of prenatal sequencing were invited to participate in semi-structured interviews about their experiences. A constructivist grounded theory approach was used to code and analyze interviews.

RESULTS

Thirty-three participants from 27 pregnancies were interviewed. Participants were motivated to enroll in the study to find out more about their fetus' condition and prepare for the future. The waiting period was a time of significant anxiety for participants. Most participants felt relief and closure upon receiving results, regardless of the category of result, and had a clear understanding of the implications of the results.

CONCLUSION

Participants' experiences with pGS were often intertwined with the experience of having a fetus with an abnormality. Participants were satisfied with the decision to participate in research and the support they received from the healthcare team, although waiting for results was associated with anxiety. The healthcare team plays an integral role in setting expectations and validating feelings of anxiety, fear and uncertainty.

Factor's that impact on women's decision-making around prenatal genomic tests: An international discrete choice survey

OBJECTIVE

We conducted a survey-based discrete-choice experiment (DCE) to understand the test features that drive women's preferences for prenatal genomic testing, and explore variation across countries.

METHODS

Five test attributes were identified as being important for decision-making through a literature review, qualitative interviews and quantitative scoring exercise. Twelve scenarios were constructed in which respondents choose between two invasive tests or no test. Women from eight countries who delivered a baby in the previous 24 months completed a DCE presenting these scenarios. Choices were modeled using conditional logit regression analysis.

RESULTS

Surveys from 1239 women (Australia: n = 178; China: n = 179; Denmark: n = 88; Netherlands: n = 177; Singapore: n = 90; Sweden: n = 178; UK: n = 174; USA: n = 175) were analyzed. The key attribute affecting preferences was a test with the highest diagnostic yield (p < 0.01). Women preferred tests with short turnaround times (p < 0.01), and tests reporting variants of uncertain significance (VUS; p < 0.01) and secondary findings (SFs; p < 0.01). Several country-specific differences were identified, including time to get a result, who explains the result, and the return of VUS and SFs.

CONCLUSION

Most women want maximum information from prenatal genomic tests, but our findings highlight country-based differences. Global consensus on how to return uncertain results is not necessarily realistic or desirable.

Study protocol: childhood outcomes of fetal genomic variants: the PrenatAL Microarray (PALM) cohort study

BACKGROUND

The implementation of genomic testing in pregnancy means that couples have access to more information about their child's genetic make-up before birth than ever before. One of the resulting challenges is the management of genetic variations with unclear clinical significance. This population-based study will help to close this critical knowledge gap through a multidisciplinary cohort study of children with and without genomic copy number variants (CNVs) diagnosed before birth. By comparing children with prenatally-ascertained CNVs to children without a CNV, we aim to (1) examine their developmental, social-emotional and health status; (2) measure the impact of prenatal diagnosis of a CNV on maternal perceptions of child health, behavior and development; and (3) determine the proportion of prenatally-ascertained CNVs of unknown or uncertain significance that are reclassified as benign or pathogenic after 2 or more years.

METHODS

This study will establish and follow up a cohort of mother-child pairs who have had a prenatal diagnosis with a chromosomal microarray from 2013-2019 in the Australian state of Victoria. Children aged 12 months to 7 years will be assessed using validated, age-appropriate measures. The primary outcome measures will be the Wechsler Preschool and Primary Scale of Intelligence IV (WPSSI-IV) IQ score (2.5 to 7 year old's), the Ages and Stages Questionnaire (12-30 months old), and the Brief Infant- Toddler Social and Emotional Assessment (BITSEA) score. Clinical assessment by a pediatrician will also be performed. Secondary outcomes will be scores obtained from the: Vineland Adaptive Behavior Scale, Maternal Postnatal Attachment Questionnaire, the Vulnerable Child Scale, Profile of Mood States, Parent Sense of Competence Scale. A descriptive analysis of the reclassification rates of CNVs after ≥2 years will be performed.

DISCUSSION

This study protocol describes the first Australian cohort study following children after prenatal diagnostic testing with chromosomal microarray. It will provide long-term outcomes of fetal genomic variants to guide evidence-based pre-and postnatal care. This, in turn, will inform future efforts to mitigate the negative consequences of conveying genomic uncertainty during pregnancy.

TRIAL REGISTRATION

ACTRN12620000446965p ; Registered on April 6, 2020.

Assessing parental understanding of variant reclassification in pediatric neurology and developmental pediatrics clinics

Improvements in technology used for genetic testing have yielded an increased numbers of variants that are identified, each with a potential to return uninformative results. While some genetics providers may expect patients to be responsible for staying abreast of updates to their genetic testing results, it is unknown whether patients are even aware of the possibility of variant reclassification. Little research has assessed the comprehension and attitudes of parents of pediatric patients regarding reclassification of variants of uncertain significance (VUS). Semi-structured telephone interviews were conducted with parents (n = 15) whose children received a VUS from genetic testing in either the pediatric neurogenetics or developmental pediatrics clinics at Riley Hospital for Children in Indianapolis, Indiana. Most participants expressed understanding of the uncertainty surrounding their child's VUS test result. However, nearly half of participants shared that they had no prior knowledge of its potential reclassification. When asked whose responsibility it is to keep informed about changes to their child's VUS status, some participants stated that it belonged solely to healthcare providers - a distinctive finding of our study - whereas others felt that it was a joint responsibility between providers and the parents. We additionally found that some patients desire a support group for individuals with VUS. These results provide insight into the importance of pretest genetic counseling and the need for increased social and informational support for parents of children who receive inconclusive genetic testing results. We conclude that relying solely on the patient or guardian to manage uncertain results may be insufficient.

Clinicians' attitudes towards parental choice in the era of advanced genomic tests in pregnancy

OBJECTIVE

Israel is one of the first countries to incorporate chromosomal microarray analysis into routine prenatal care. We explored attitudes of Israeli healthcare professionals (HCPs) towards the disclosure of challenging findings: variants of uncertain clinical significance (VUS), susceptibility loci (SL) for neurodevelopmental disorders and variants associated with adult-onset (AO) conditions. Particularly, we sought their views on providing parental choice regarding the disclosure of these findings.

METHODS

Twenty-nine in-depth interviews were conducted with genetic counselors (n = 19), medical geneticists (n = 4), medical geneticists that are trained in and practice fetal medicine (n = 3), and fetal medicine experts (n = 3).

RESULTS

Most participants (n = 24) supported parental choice regarding uncertain genetic information. Engaging parents in disclosure decisions allows avoidance from potentially anxiety-provoking information, practicing parental autonomy, and better preparation in cases where uncertain findings are identified. HCPs believed that given appropriate preparation, parents can make informed decisions. Four participants believed that disclosure should be based on professional judgment and one supported full-disclosure. Unlike VUS or SL, all interviewees agreed that in cases of medically actionable AO conditions, the benefit of disclosure outweighs the damage.

CONCLUSION

HCPs attitudes are largely in-line with the Israeli practice of involving parents in disclosure decisions regarding uncertain information. This may mitigate disclosure dilemmas and allow personalized disclosure based on parents' views.

Prenatal chromosome microarray: 'The UK experience'. A survey of reporting practices in UK genetic services (2012-2019)

BACKGROUND

The value of chromosome microarray (CMA) in the prenatal detection of significant chromosome anomalies is well-established. To guide the introduction of this technique in routine clinical practice, the Joint Committee on Genomics in Medicine developed national UK guidelines for reporting prenatal CMA in 2015.

OBJECTIVE

To evaluate the UK experience of utilising prenatal CMA.

METHOD

A 36-item survey was distributed to all UK clinical genetics services (n = 23) in March 2019 requesting information pertaining to experience since diagnostic testing commenced and current practice (March 2018 to March 2019).

RESULTS

Eighteen UK genetics services currently offer prenatal CMA. A total of 14,554 tests had been performed. A pathogenic copy number variant was identified in 7.8% of tests overall, though the diagnostic rate increased to 8.4% in the final year of the survey. Variants of uncertain significance (VUS) were reported in 0.7% of tests, and 'actionable' incidental findings in 0.12%.

CONCLUSION

Diagnostic rate has improved over time, while reporting of VUS has decreased. Reviewing survey responses at a national level highlights variation in testing experience and practice, raising considerations both for future guideline development and implementation of other novel techniques including prenatal whole exome sequencing.

Performance of Chromosomal Microarray Analysis for Detection of Copy Number Variations in Fetal Echogenic Bowel

BACKGROUND

Fetal echogenic bowel (FEB) is associated with an increased risk of poor pregnant outcomes; however, karyotyping fails to detect copy number variations (CNVs) in FEB. This study aimed to evaluate the performance of chromosomal microarray analysis (CMA) for detection of FEB.

METHODS

The medical records of 147 pregnant women with FEB recruited during December 2015 to December 2018 were retrospectively reviewed, and prenatal samples were collected for karyotyping and CMA. The detection of chromosomal abnormality was compared between karyotyping and CMA.

RESULTS

Karyotyping identified eight cases with abnormal karyotypes (5.44% prevalence), including four fetuses with pathogenic aneuploidy, three with chromosome polymorphism and one with balanced chromosome translocation. CMA identified 13 abnormal CNVs (8.84% prevalence), including 4 fetuses with pathogenic aneuploidy as detected by karyotyping and 9 additional CNVs with normal karyotypes; however, CMA failed to detect chromosome polymorphism and balanced chromosome translocation. In fetuses with isolated FEB, no cases presented pathogenic findings and CMA detected two cases with variants of uncertain significance (VOUS). In cases presenting FEB along with other ultrasound abnormalities, CMA detected three cases with pathogenic CNVs and four cases with VOUS in addition to four cases with aneuploidy. There was no significant difference in the detection of abnormal CNVs between the fetuses with echogenic bowel alone and along with other ultrasound abnormalities (10% vs 8.67%, P > 0.05). Except 9 fetuses lost to the follow-up, the other 138 fetuses with echogenic bowel were successfully followed up. Pregnancy was terminated in 5 fetuses with chromosomal abnormality, 2 with pathogenic CNVs and 1 with VOUS, and other 16 with normal karyotypes and CMA findings but showing ultrasound abnormalities or multiple malformations.

CONCLUSION

Isolated FEB is associated with a good prognosis, and a satisfactory pregnant outcome is expected for fetuses with echogenic bowel that are negative for chromosomal anomalies and other severe structure abnormalities. CMA shows an important value in the genetic diagnosis of FEB. As a supplement to karyotyping, CMA may improve the accuracy of prenatal diagnosis of fetal intestinal malformations in pregnant women with FEB.

How are uncertain prenatal genetic results perceived and managed two years after they were received? A qualitative interview study

Chromosomal microarray has considerably improved our ability to identify or dismiss genetic conditions in the unborn child. However, this detailed analysis also reveals copy number variants (CNVs) of unknown or uncertain significance, in which the specific child's prognosis can be difficult to predict. Little is known about the longer-term impacts of receiving an uncertain prenatal CNV result. Our qualitative study explored how such a result was perceived and managed in everyday life, 2 years after it was received. From an original sample of 16 couples, nine women participated in a semi-structured follow-up phone interview. Transcripts were analyzed using thematic analysis. The results show that these women did not perceive the CNV result to be a part of their everyday lives. They managed the CNV result by focusing on the child's positive development, by not sharing the CNV information in wider social networks, and by emphasizing parental values such as taking life as it comes, welcoming human variation, and accepting that dealing with a child's struggles is an inherent part of parenthood. Overall, the women expressed a positive attitude toward prenatal genetic information about serious disorders but considered 'their' CNV to be close to normal; several women suggested that such findings should not be reported. However, they also recognized the difficulties in making such decisions, given variable penetrance and that couples' definitions of 'serious' could vary significantly. The diagnostic process during pregnancy was remembered as being highly stressful, and many expressed a need for more control in a future pregnancy. Our study provides insight into how mothers reconfigure CNV results to fit their values and everyday lives. When delivering uncertain CNV results in a prenatal setting, genetics healthcare providers should present and discuss long-term coping strategies with expecting parents.

The Expert in the Room: Parental Advocacy for Children with Sex Chromosome Aneuploidies

OBJECTIVE

Owing to fragmentation in the medical system, many parents of children with disabilities report taking on a care coordinator and advocate role. The parental advocacy and care coordination requirements are further amplified in this population because of a lack of awareness about sex chromosome aneuploidies (SCAs) in medical and social services settings, as well as the complex needs of affected children. This burden disproportionately affects mothers and low-resource families as a result of gendered ideas of parenthood and social stratification in resource access. The aim of this study is to understand the unique parental burdens of SCAs and family support needs.

METHODS

We conducted 43 interviews with individuals with SCAs and/or their parents and qualitatively coded and analyzed the transcripts for themes relating to parent advocacy, medical services, social and educational services, and coping.

RESULTS

Our findings indicate that parents must repeatedly advocate for their concerns about their child to be taken seriously before diagnosis and continue to advocate for services and interventions throughout childhood and adolescence. Parents also report the need to educate health care professionals about their child's medical condition. A majority of the parent participants were women, and single mothers reported high levels of emotional burden.

CONCLUSION

Parents of children with SCAs shoulder additional roles of medical advocate and care coordinator. This causes excessive burden on families but also disadvantages families in which parents are unable to act as an advocate for their child.

Dealing with uncertain results from chromosomal microarray and exome sequencing in the prenatal setting: An international cross-sectional study with healthcare professionals

Objectives

To conduct qualitative interviews with healthcare providers working in different countries to understand their experiences of dealing with uncertain results from prenatal chromosome microarray analysis (CMA) and exome sequencing (ES).

Methods

Semi‐structured interviews with 31 healthcare providers who report or return prenatal CMA and/or ES results (clinicians, genetic counsellors and clinical scientists) in six countries with differing healthcare systems; Australia (4), Denmark (5), Netherlands (6), Singapore (4), Sweden (6) and United Kingdom (6). The topic guide explored the main sources of uncertainty and their management.

Results

There was variation in reporting practices both between and across countries for variants of uncertain significance, however, there was broad agreement on reporting practices for incidental findings. There was also variation in who decides what results are reported (clinical scientists or clinicians). Technical limitations and lack of knowledge (to classify variants and of prenatal phenotypes) were significant challenges, as were turnaround times and lack of guidelines.

Conclusion

Health professionals around the globe are dealing with similar sources of uncertainty, but managing them in different ways, Continued dialogue with international colleagues on ways of managing uncertain results is important to compare and contrast the benefits and limitations of the different approaches.

What's already known about this topic?

Chromosome microarray analysis and exome sequencing have increased diagnostic yield over karyotyping but have increased the incidence of uncertain results.

What does this study add?

Our findings highlight variation in reporting practices both between and across countries for variants of uncertain significance, although there is broad agreement on reporting practices for incidental findings.

International guidelines may help to standardise how we define and categorise variants, however, global uniformity on the management of uncertain results may not be a realistic or desirable goal.

Utility of Genetic Testing from the Perspective of Parents/Caregivers: A Scoping Review

In genomics, perceived and personal utility have been proposed as constructs of value that include the subjective meanings and uses of genetic testing. Precisely what constitutes these constructs of utility and how they vary by stakeholder perspective remains unresolved. To advance methods for measuring the value of genetic testing in child health, we conducted a scoping review of the literature to characterize utility from the perspective of parents/caregivers. Peer reviewed literature that included empiric findings from parents/caregivers who received genetic test results for an index child and was written in English from 2016-2020 was included. Identified concepts of utility were coded according to Kohler's construct of personal utility. Of 2142 abstracts screened, 33 met inclusion criteria. Studies reflected a range of genetic test types; the majority of testing was pursued for children with developmental or neurodevelopmental concerns. Coding resulted in 15 elements of utility that mapped to Kohler's four domains of personal utility (affective, cognitive, behavioural and social) and one additional medical management domain. An adapted construct of utility for parents/caregivers may enable specific and standardized strategies for researchers to use to generate evidence of the post-test value of genetic testing. In turn, this will contribute to emerging methods for health technology assessment and policy decision making for genomics in child health.

Parental experiences of uncertainty following an abnormal fetal anomaly scan: Insights using Han's taxonomy of uncertainty

For a number of prospective parents, uncertainty during pregnancy starts when an anomaly is found during a routine fetal anomaly scan. This may be followed by numerous tests to determine the etiology and nature of the anomaly. In this study, we aimed to understand how prospective parents perceive and manage uncertainty after being confronted with a structural anomaly during their routine ultrasound. Han's taxonomy of uncertainty was used as a framework to identify and understand the different types of uncertainty experienced. Interviews were held in the UK (n = 8 women and n = 1 male partner) and in the Netherlands (n = 7 women) with participants who had experienced uncertainty in their pregnancy after a fetal scan. Data were analyzed using thematic analysis, and the uncertainties experienced by parents were mapped against the dimensions of the Han taxonomy (sources, issues, and locus). Participants' experience of uncertainty was relevant to all dimensions and subcategories of the Han taxonomy, showing its applicability in the prenatal setting. Sources of uncertainty included receiving probabilistic or ambiguous information about the anomaly, or information that was complex and challenging to understand. Issues of uncertainty included were those that were scientific—such as a probable diagnosis with no further information, personal—such as the emotional impact of uncertainty, and practical—such as limited information about medical procedures and practical aspects of care. Additionally, participants described what helped them to manage uncertainty. This included active coping strategies such as searching for information on the Internet, external coping resources such as seeking social support, and internal coping resources such as using positivity and hope. Several recommendations for the healthcare professional to minimize uncertainty and help the patient deal with uncertainty have been proposed based on these findings.

Couples experiences of receiving uncertain results following prenatal microarray or exome sequencing: A mixed-methods systematic review

Background

Tests in pregnancy such as chromosomal microarray analysis and exome sequencing are increasing diagnostic yield for fetal structural anomalies, but have greater potential to result in uncertain findings. This systematic review investigated the experiences of prospective parents about receiving uncertain results from these tests.

Methods

A systematic search of three electronic databases was conducted. Data extraction was performed for studies that met the eligibility and quality criteria. Results were synthesised following the principles of thematic analysis.

Results

Fourteen studies (10 qualitative, 4 quantitative) were included. Findings were grouped into three overarching themes. Sources of uncertainty included the testing procedure, the diagnosis and prognosis, and health professionals' own uncertainty. The clinical impact of the uncertainty included parents struggling to make clinical decisions with the information available, the emotional impact included decisional‐regret, shock, worry and feeling overwhelmed. To manage the uncertainty, parents sought support from healthcare professionals, friends, family, the internet and other parents as well as remaining hopeful.

Conclusions

Prospective parents experience a myriad of uncertainties in the prenatal setting, which must be handled sensitively. Future research should explore optimal ways of managing uncertainty to minimise harm. Recommendations are made for discussing uncertainty during pre‐ and post‐test counseling.

Adult patients with undiagnosed conditions and their responses to unresolved uncertainty from exome sequencing

Patients pursuing exome sequencing (ES) in their quest for diagnosis will most often experience unresolved uncertainty from their ES results because the majority of ES results are non-diagnostic. This study explored and compared the experiences of receiving two types of ES results that may result in diagnostic uncertainty. Semi-structured phone interviews were conducted with 23 adult patients with undiagnosed conditions who received either a negative result or a result with one or more variants of uncertain significance (VUSs) from ES. Interviews were transcribed and subjected to thematic and comparative analyses. Participants accurately understood their results and described various sources of genomic uncertainty including probability, complexity, and ambiguity. Their acclimation to illness uncertainty resulted in realistic expectations about and acceptance of their results. Participants still hoped that ES would end their diagnostic odyssey. Hope and optimism were used to cope with continued uncertainty. No thematic differences were found between the experiences of those who received negative results versus those who received VUSs. Our findings may inform clinical practices of informed consent and disclosure of negative results and VUSs through a greater consideration of patients' reactions, concerns, and challenges with adaptation to uncertainty.

"It's probably nothing, but…" Couples' experiences of pregnancy following an uncertain prenatal genetic result

INTRODUCTION

A common concern regarding the introduction of chromosomal microarray in prenatal testing is the concomitant identification of an uncertain copy number variant (CNV) where significance and clinical implication for the unborn child can be difficult or impossible to predict. Following the identification of an uncertain CNV, prospective parents may decide to continue the pregnancy. The aim of this study was to explore how prospective parents manage uncertainty and experience pregnancy in light of an uncertain CNV result.

MATERIAL AND METHODS

Qualitative interviews with 16 women and 10 partners who had received a prenatally diagnosed, uncertain CNV. Participants were recruited from the Aarhus University Hospital, Denmark and most were interviewed in their homes 1-14 weeks after birth. Data were analyzed using thematic analysis.

RESULTS

Following the CNV diagnosis, some couples focused on the severe syndromes ruled out by the result, whereas others were more concerned with the new potential risks, for example, learning disabilities. Most couples did not remember the actual diagnosis, but all described a number of attention points generated by the CNV result. During pregnancy, the couples used various strategies to limit worry and enjoy their pregnancy, such as limiting information seeking, reducing talk of the CNV, and deferring thoughts of potential consequences. Furthermore, ultrasound was considered a valuable resource for reducing worry as it provided reassurance about the development of the baby. Inherited CNVs caused relief on one hand, but also feelings of responsibility for the child's potential challenges. After birth, worry decreased considerably, but all couples paid some extra attention to the child's development, while also being alert to the risk of wrongfully interpreting the child's development in terms of the CNV. Eleven couples expressed satisfaction with knowing about the child's CNV, whereas five couples would rather not have known.

CONCLUSIONS

The results indicate that health professionals should be mindful of terminology, remember to point out what has been ruled out by the CNV result, and discuss potential coping strategies with the couple. Furthermore, these couples may have a higher need for ultrasound during pregnancy to help reduce worry. More research is needed on the families' long-term coping.

C-banding and AgNOR-staining were still effective complementary methods to indentify chromosomal heteromorphisms and some structural abnormalities in prenatal diagnosis

BACKGROUND

In prenatal diagnosis, CMA has begun to emerge as a favorable alternative to karyotype analysis, but it could not identify balanced translocations, triploidies, inversion and heteromorphisms. Therefore, conventional cytogenetic and specific staining methods still play an important role in the work-up of chromosome anomaly. This study investigated the application of C-banding and AgNOR-staining techniques in prenatal diagnosis of chromosomal heteromorphisms and some structure abnormalities.

RESULTS

Among the 2970 samples, the incidence of chromosomal heteromorphisms was 8.79% (261/2970). The most frequent was found to be chromosome Y (2.93%, 87/2970), followed by chromosome 1 (1.65 %, 49/2970), 9 (1.52 %, 45/2970), 22 (0.77 %, 23/2970) and 15 (0.64 %, 19/2970). We compared the incidence of chromosomal heteromorphisms between recurrent spontaneous abortion (RSA) group and control group. The frequency of autosomal hetermorphisms in RSA group was 7.63% higher than that in control group (5.78%), while the frequency of Y chromosomal heteromorphisms was 4.76% lower than that in control group (5.71%). Here we summarized 4 representative cases, inv (1) (p12q24), psu dic (4;17) (p16.3;p13.3), r(X)(p11; q21) and an isodicentric bisatellited chromosome to illustrate the application of C-banding or AgNOR-staining, CMA or NGS was performed to detect CNVs if necessary.

CONCLUSIONS

This study indicated that C-banding and AgNOR-staining were still effective complementary methods to identify chromosomal heteromorphisms and marker chromosomes or some structural rearrangements involving the centromere or acrocentric chromosomes. Our results suggested that there was no evidence for an association between chromosomal heteromorphisms and infertility or recurrent spontaneous abortions. Undoubtedly, sometimes we needed to combine the results of CMA or CNV-seq to comprehensively reflect the structure and aberration of chromosome segments. Thus, accurate karyotype reports and genetic counseling could be provided.

The Frog Xenopus as a Model to Study Joubert Syndrome: The Case of a Human Patient With Compound Heterozygous Variants in PIBF1

Joubert syndrome (JS) is a congenital autosomal-recessive or—in rare cases–X-linked inherited disease. The diagnostic hallmark of the so-called molar tooth sign describes the morphological manifestation of the mid- and hind-brain in axial brain scans. Affected individuals show delayed development, intellectual disability, ataxia, hyperpnea, sleep apnea, abnormal eye, and tongue movements as well as hypotonia. At the cellular level, JS is associated with the compromised biogenesis of sensory cilia, which identifies JS as a member of the large group of ciliopathies. Here we report on the identification of novel compound heterozygous variants (p.Y503C and p.Q485^*) in the centrosomal gene PIBF1 in a patient with JS via trio whole exome sequencing. We have studied the underlying disease mechanism in the frog Xenopus, which offers fast assessment of cilia functions in a number of embryological contexts. Morpholino oligomer (MO) mediated knockdown of the orthologous Xenopus pibf1 gene resulted in defective mucociliary clearance in the larval epidermis, due to reduced cilia numbers and motility on multiciliated cells. To functionally assess patient alleles, mutations were analyzed in the larval skin: the p.Q485^* nonsense mutation resulted in a disturbed localization of PIBF1 to the ciliary base. This mutant failed to rescue the ciliation phenotype following knockdown of endogenous pibf1. In contrast, the missense variant p.Y503C resulted in attenuated rescue capacity compared to the wild type allele. Based on these results, we conclude that in the case of this patient, JS is the result of a pathogenic combination of an amorphic and a hypomorphic PIBF1 allele. Our study underscores the versatility of the Xenopus model to study ciliopathies such as JS in a rapid and cost-effective manner, which should render this animal model attractive for future studies of human ciliopathies.