Biallelic KIF24 Variants Are Responsible for a Spectrum of Skeletal Disorders Ranging From Lethal Skeletal Ciliopathy to Severe Acromesomelic Dysplasia

Skeletal dysplasias comprise a large spectrum of mostly monogenic disorders affecting bone growth, patterning, and homeostasis, and ranging in severity from lethal to mild phenotypes. This study aimed to underpin the genetic cause of skeletal dysplasia in three unrelated families with variable skeletal manifestations. The six affected individuals from three families had severe short stature with extreme shortening of forelimbs, short long-bones, and metatarsals, and brachydactyly (family 1); mild short stature, platyspondyly, and metaphyseal irregularities (family 2); or a prenatally lethal skeletal dysplasia with kidney features suggestive of a ciliopathy (family 3). Genetic studies by whole genome, whole exome, and ciliome panel sequencing identified in all affected individuals biallelic missense variants in KIF24, which encodes a kinesin family member controlling ciliogenesis. In families 1 and 3, with the more severe phenotype, the affected subjects harbored homozygous variants (c.1457A>G; p.(Ile486Val) and c.1565A>G; p.(Asn522Ser), respectively) in the motor domain which plays a crucial role in KIF24 function. In family 2, compound heterozygous variants (c.1697C>T; p.(Ser566Phe)/c.1811C>T; p.(Thr604Met)) were found C-terminal to the motor domain, in agreement with a genotype-phenotype correlation. In vitro experiments performed on amnioblasts of one affected fetus from family 3 showed that primary cilia assembly was severely impaired, and that cytokinesis was also affected. In conclusion, our study describes novel forms of skeletal dysplasia associated with biallelic variants in KIF24. To our knowledge this is the first report implicating KIF24 variants as the cause of a skeletal dysplasia, thereby extending the genetic heterogeneity and the phenotypic spectrum of rare bone disorders and underscoring the wide range of monogenetic skeletal ciliopathies. (c) 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).Peer reviewe

Clinical impact of additional findings detected by genome-wide non-invasive prenatal testing:Follow-up results of the TRIDENT-2 study

In the TRIDENT-2 study, all pregnant women in the Netherlands are offered genome-wide non-invasive prenatal testing (GW-NIPT) with a choice of receiving either full screening or screening solely for common trisomies. Previous data showed that GW-NIPT can reliably detect common trisomies in the general obstetric population and that this test can also detect other chromosomal abnormalities (additional findings). However, evidence regarding the clinical impact of screening for additional findings is lacking. Therefore, we present follow-up results of the TRIDENT-2 study to determine this clinical impact based on the laboratory and perinatal outcomes of cases with additional findings. Between April 2017 and April 2019, additional findings were detected in 402/110,739 pregnancies (0.36%). For 358 cases, the origin was proven to be either fetal (n = 79; 22.1%), (assumed) confined placental mosaicism (CPM) (n = 189; 52.8%), or maternal (n = 90; 25.1%). For the remaining 44 (10.9%), the origin of the aberration could not be determined. Most fetal chromosomal aberrations were pathogenic and associated with severe clinical phenotypes (61/79; 77.2%). For CPM cases, occurrence of pre-eclampsia (8.5% [16/189] vs 0.5% [754/159,924]; RR 18.5), and birth weigh

Inequalities in uptake of prenatal screening according to ethnicity and socio-economic status in the four largest cities of the Netherlands (2011-2013)

OBJECTIVES: In the Netherlands, all women are claimed to have equal access to prenatal screening (PS). Prior research demonstrated substantial inequalities in PS uptake associated with socioeconomic status (SES) and ethnic background. The suggested pathway was a lack of intention to participate in PS among these subgroups. We studied the background of inequalities in PS participation, challenging intention heterogeneity as the single explanation. METHODS: Multivariable logistic regression analyses of the national PS registry, focusing on the four largest cities in the Netherlands (n = 4578, years 2011-2013), stratified by SES. OUTCOME MEASURES: (1) any uptake of PS (yes/no) and (2) uptake (one/two tests) for women who intended to participate in two tests. Determinants included intention, ethnicity, practice, and age. RESULTS: Of non-Western women, 85.7% were screened versus 89.7% of Western women. Intention was an important explanatory factor in all models. However, after correction for intention, ethnicity remained a significant determinant for differences in uptake. Ethnicity and SES also interacted, indicating that non-Western women in low SES areas had the lowest uptake (corrected for intention). CONCLUSIONS FOR PRACTICE: Socioeconomic status and ethnicity related inequalities in PS uptake are only partially explained by intention heterogeneity; other pathways, in particular provider-related determinants, may play a role. © 2017 John Wiley & Sons, Ltd

Limited additional value of karyotyping cultured amniotic fluid cell colonies in addition to microarray on uncultured cells for confirmation of abnormal non-invasive prenatal testing results

Objectives: Non-invasive prenatal testing (NIPT) allows the detection of placental chromosome aberrations. To verify whether the fetus also has the chromosome aberration, diagnostic follow-up testing is required. The aim of this retrospective study was to assess the added value of analyzing amniotic fluid (AF) cell cultures in addition to uncultured AF cells for the detection of fetal mosaicism. Method: NIPT was performed as part of the Dutch TRIDENT study. Cytogenetic studies in uncultured AF were performed using single nucleotide polymorphism (SNP)-array. Cultured AF cell colonies (in situ method) were investigated with fluorescent in situ hybridization and/or karyotyping. Clinical outcome data were collected in cases with discordant results. Results: Between April 2014 and December 2021, 368 amniocenteses were performed after a chromosomal aberration was detected with NIPT. Excluding 134 cases of common aneuploidies (confirmed by quantitative fluorescence polymerase chain reaction), 29 cases with investigation of uncultured cells only and 1 case without informed consent, 204 cases were eligible for this study. In 196 (96%) cases, the results in uncultured and cultured cells were concordant normal, abnormal or mosaic. Five cases (2%) showed mosaicism in cultured AF cells, whereas uncultured AF cells were normal. Two (1%) of these, one mosaic trisomy 13 and one mosaic trisomy 16, were considered true fetal mosaics. Conclusion: The added value of investigating AF cell cultures in addition to uncultured cells is limited to two of 204 (1%) cases in which true fetal mosaicsm would otherwise be missed. The clinical relevance of one (trisomy 13) remained unknown and the other case also showed ultrasound anomalies, which determined pregnancy management. This seems to justify limiting prenatal cytogenetic confirmatory testing to SNP arrays on uncultured AF cells, considerably shortening the reporting time.</p

The Psychological Challenges of Replacing Conventional Karyotyping with Genomic SNP Array Analysis in Prenatal Testing

Pregnant couples tend to prefer a maximum of information about the health of their fetus. Therefore, we implemented whole genome microarray instead of conventional karyotyping (CK) for all indications for prenatal diagnosis (PND). The array detects more clinically relevant anomalies, including early onset disorders, not related to the indication and more genetic anomalies of yet unquantifiable risk, so-called susceptibility loci (SL) for mainly neurodevelopmental disorders. This manuscript highlights the psychological challenges in prenatal genetic counselling when using the array and provides counselling suggestions. First, we suggest that pre-test decision counselling should emphasize deliberation about what pregnant couples wish to learn about the future health of their fetus more than information about possible outcomes. Second, pregnant couples need support in dealing with SL. Therefore, in order to consider the SL in a proportionate perspective, the presence of phenotypes associated with SL in the family, the incidence of a particular SL in control populations and in postnatally ascertained patients needs highlighting during post-test genetic counselling. Finally, the decision that couples need to make about the course of their pregnancy is more complicated when the expected phenotype is variable and not quantifiable. Therefore, during post-test psychological counseling, couples should concretize the options of continuing and ending their pregnancy; all underlying feelings and thoughts should be made explicit, as well as the couple’s resources, in order to attain adequate decision-making. As such, pre- and post-test counselling aids pregnant couples in handling the uncertainties that may accompany offering a broader scope of genetic PND using the array

What proportion of couples with a history of recurrent pregnancy loss and with a balanced rearrangement in one parent can potentially be identified through cell-free DNA genotyping?

Abstract Background Balanced chromosome aberrations are reported in about 1:30 couples with recurrent pregnancy loss (RPL). Karyotyping of both parents is necessary to identify these aberrations. Genome-wide non-invasive prenatal testing (NIPT) in case of recurrent pregnancy loss could be a more efficient way to identify couples at increased risk for carrying a balanced chromosome rearrangement. The aim of this study was to evaluate whether the potential fetal imbalances caused by parental balanced aberrations detected in our center are large enough to be detectable by genome-wide non-invasive prenatal testing (NIPT). Material and methods From January 1970 until May 2020 our laboratory received 30,863 unique requests for karyotyping due to RPL. We have identified 16,045 couples and evaluated all abnormal cytogenetic results to assess the minimal size of the involved chromosomal segments in potential unbalanced products of the rearrangements. Results In the presented cohort we detected 277 aberrant balanced translocations/inversions in females and 185 in males amongst 16,045 couples with RPL, which can be translated to a risk of 1:35 (2.9%, 95% CI 2.6–3.2%). Our study showed that the vast majority (98.7%, 95% CI 97.1–99.5%) of these balanced aberrations will potentially cause a fetal imbalance > 10 Mb, which is detectable with genome-wide NIPT if it was performed during one of the miscarriages. Conclusions Our study suggests that genome-wide NIPT is able to reveal most unbalanced products of balanced chromosomal rearrangements carried by couples with RPL and therefore can potentially identify balanced chromosomal aberration carriers. Moreover, our data suggest that these couples can be offered NIPT in case they decline invasive testing in future pregnancies

Prenatal ultrasound finding of atypical genitalia: Counseling, genetic testing and outcomes

Objective: To report uptake of genetic counseling (GC) and prenatal genetic testing after the finding of atypical genitalia on prenatal ultrasound (US) and the clinical and genetic findings of these pregnancies. Methods: A retrospective cohort study (2017–2019) of atypical fetal genitalia in a large expert center for disorders/differences of sex development. We describe counseling aspects, invasive prenatal testing, genetic and clinical outcome of fetuses apparently without [group 1, n = 22 (38%)] or with [group 2, n = 36 (62%)] additional anomalies on US. Results: In group 1, 86% of parents opted for GC versus 72% in group 2, and respectively 58% and 15% of these parents refrained from invasive testing. Atypical genitalia were postnatally confirmed in 91% (group 1) and 64% (group 2), indicating a high rate of false positive US diagnosis of ambiguous genitalia. Four genetic diagnoses were established in group 1 (18%) and 10 in group 2 (28%). The total genetic diagnostic yield was 24%. No terminations of pregnancy occurred in group 1. Conclusions: For optimal care, referral for an expert fetal US scan, GC and invasive diagnostics including broad testing should be offered after prenatal detection of isolated atypical genitalia

Early embryonic development from zygote to blastocyst.

<p>The cytotrophoblast which is studied in short-term cultured villi (STC-villi) and with NIPT is derived from the trophoblast of the blastocyst, whereas the mesenchymal core, investigated in long-term cultured villi (LTC-villi) originates from the extra-embryonic mesoderm (EEM). Both EEM and fetus are derived from the inner cell mass (ICM) of the blastocyst.</p