To investigate the role of DNA topoisomerases in transcription, we have studied global gene expression in Saccharomyces cerevisiae cells deficient for topoisomerases I and II and performed single-gene analyses to support our findings. The genome-wide studies show a general transcriptional down-regulation upon lack of the enzymes, which correlates with gene activity but not gene length. Furthermore, our data reveal a distinct subclass of genes with a strong requirement for topoisomerases. These genes are characterized by high transcriptional plasticity, chromatin regulation, TATA box presence, and enrichment of a nucleosome at a critical position in the promoter region, in line with a repressible/inducible mode of regulation. Single-gene studies with a range of genes belonging to this group demonstrate that topoisomerases play an important role during activation of these genes. Subsequent in-depth analysis of the inducible PHO5 gene reveals that topoisomerases are essential for binding of the Pho4p transcription factor to the PHO5 promoter, which is required for promoter nucleosome removal during activation. In contrast, topoisomerases are dispensable for constitutive transcription initiation and elongation of PHO5, as well as the nuclear entrance of Pho4p. Finally, we provide evidence that topoisomerases are required to maintain the PHO5 promoter in a superhelical state, which is competent for proper activation. In conclusion, our results reveal a hitherto unknown function of topoisomerases during transcriptional activation of genes with a repressible/inducible mode of regulation.

Introduction:Applying whole-exome sequencing (WES) for the diagnosis of diseases in children has shown significant diagnostic strength compared with chromosomal microarray. WES may also have the potential of adding clinically relevant prenatal information in cases where a fetus is found to have structural anomalies. We present results from the first fetal exomes performed in a tertiary center in Denmark. Material and methods: Couples/expectant parents were included in Central DenmarkRegion from July 2016 to March 2019. Inclusion was not systematic, but where one or more fetal malformations or severe fetal hydrops were detected, and a specific diagnosis had not been obtained by chromosomal microarray. WES was performed in ongoing pregnancies (N = 11), after intrauterine demise (N = 5), or after termination of pregnancy based on ultrasound findings (N = 19). In most cases, a trio format was applied comprising fetal and parental DNA.Results: WES was performed in 35 highly selected fetal cases. Pathogenic variants, or variants likely to explain the phenotype, were detected in 9/35 (26%). Variants of uncertain significance were detected in 7/35 (20%) and there was one secondary finding (3%). Out of the 11 ongoing pregnancies, four reached a genetic diagnosis (36%). Detection rate was highest in cases of multisystem anomalies (7/13, 54%).WES was completed in all three trimesters and both autosomal dominant, autosomal recessive and X-linked inheritance were revealed. Conclusions:We present data from 35 cases of exome sequencing applied in a setting of fetal malformations. Importantly, though, we wish to share our personal experiences with implementing WES into a prenatal setting. As a medical society, we must continue to share what we do not understand, what went wrong, what is difficult, and what we do not agree upon. A common understanding and language are warranted. We also advocate that more research is needed concerning the clinical value, as well as costs and patient perspectives, of using WES in pregnancy. We believe that WES will lead to improved prenatal and perinatal care. How to cite this article: Becher N, Andreasen L, Sandager P, et al. Implementation of exome sequencing in fetal diagnostics-Data and experiences from a tertiary center in Denmark. Acta Obstet Gynecol Scand. 2020;99:783-790.

Mutations in the human cadherin 23 (CDH23) gene cause deafness, neurosensory, autosomal recessive 12 (DFNB12) nonsyndromic hearing loss or Usher syndrome, type 1D (characterized by hearing impairment, vestibular dysfunction, and visual impairment). Reported waltzer mouse strains each harbor a Cdh23-null mutation and present with hearing loss and vestibular dysfunction. Two additional Cdh23 mouse mutants, salsa and erlong, each carry a homozygous Cdh23 missense mutation and have progressive hearing loss. We report the identification of a novel mouse strain, jera, with inherited hearing loss caused by an N-ethyl-N-nitrosourea-induced c.7079T>A mutation in the Cdh23 gene. The mutation generates a missense change, p.V2360E, in Cdh23. Affected mice have profound sensorineural deafness, with no vestibular dysfunction. The p.V2360E mutation is semidominant because heterozygous mice have milder and more progressive hearing loss in advanced age. The mutation affects a highly conserved Ca 2؉ -binding motif in extracellular domain 22, thought to be important for Cdh23 structure and dimerization. Molecular modeling suggests that the Cdh23 V2360E/V2360E mutation alters the structural conformation of the protein and affects Ca 2؉ -binding properties. Similar to salsa mice, but in contrast to waltzer mice, hair bundle development is normal in jera and hearing loss appears to be due to the loss of tip links. Thus, jera is a novel mouse model for DFNB12. (Am J Pathol 2011, 179:903-914;

Background: Cell-free NIPT and cell-based NIPT are risk-free testing options using maternal blood samples to screen for fetal aneuploidies, but the methods differ. For cell-free NIPT, the fetal fraction of cell-free DNA in plasma is analyzed with a high background of maternal DNA. In contrast, for cell-based NIPT, a limited number of the rare, intact fetal cells are isolated for the genetic analysis. This case demonstrates the differences regarding testing for fetal sex-chromosomes anomalies (SCAs) between these two tests.Materials and Methods: A pregnant woman with mosaicism for Turner syndrome opted for NIPT in first trimester. For the cell-free NIPT analysis, DNA extraction, genome-wide massive parallel sequencing, and data analysis were carried out as described by the kit manufacturer (Illumina©, San Diego, CA, USA). For cell-based NIPT, the first sample gave no result, but the woman consented to repeat cell-based NIPT. After whole genome amplification and STR analysis, fetal DNA from three individual fetal cells was subjected to chromosomal microarray (aCGH, Agilent oligoarray, 180 kb).Results: Fetal fraction was 7%, and cell-free NIPT showed 2 copies of chromosomes 13, 18, and 21 and a decreased proportion of chromosome X, suggestive of fetal Turner syndrome. In contrast, the cell-based NIPT result showed no aneuploidy and two X-chromosomes in the fetus.Conclusion: cell-based NIPT may provide a non-invasive testing option to screen for SCAs in women with mosaicism for monosomy-X in blood, where cell-free NIPT cannot discriminate whether the X-loss is maternal or fetal.