Novel deletion of exon 3 in TYR gene causing Oculocutaneous albinism 1B in an Indian family along with intellectual disability associated with chromosomal copy number variations

Background Oculocutaneous albinism (OCA) is an autosomal recessive disorder characterized by hypo-pigmentation of skin, hair, and eyes. The OCA clinical presentation is due to a deficiency of melanin biosynthesis. Intellectual disability (ID) in OCA cases is a rare clinical presentation and appropriate diagnosis of ID is challenging through clinical examination. We report an Indian family with a rare co-inheritance of OCA1B and ID due to a novel TYR gene variant and chromosomal copy number variations. Methods We have done a study on three siblings (2 males and 1 female) of a family where all of them presented with hypopigmented skin, hair and eyes. The male children and their father was affected with ID. Targeted exome sequencing and multiplex ligation-dependent probe amplification analysis were carried out to identify the OCA1B and ID associated genomic changes. Further Array-CGH was performed using SurePrint G3 Human CGH + SNP, 8*60 K array. Results A rare homozygous deletion of exon 3 in TYR gene causing OCA1B was identified in all three children. The parents were found to be heterozygous carriers. The Array-CGH analysis revealed paternally inherited heterozygous deletion(1.9 MB) of 15q11.1-> 15q11.2 region in all three children. Additionally, paternally inherited heterozygous deletion(2.6 MB)of 10q23.2-> 10q23.31 region was identified in the first male child; this may be associated with ID as the father and the child both presented with ID. While the 2nd male child had a denovo duplication of 13q31.1-> 13q31.3 chromosomal region. Conclusion A rare homozygous TYR gene exon 3 deletion in the present study is the cause of OCA1B in all three children, and the additional copy number variations are associated with the ID. The study highlights the importance of combinational genetic approaches for diagnosing two different co-inherited disorders (OCA and ID). Hence, OCA cases with additional clinical presentation need to be studied in-depth forthe appropriate management of the disease.

Chromosomal copy number heterogeneity predicts survival rates across cancers

Survival rates of cancer patients vary widely within and between malignancies. While genetic aberrations are at the root of all cancers, individual genomic features cannot explain these distinct disease outcomes. In contrast, intra-tumour heterogeneity (ITH) has the potential to elucidate pan-cancer survival rates and the biology that drives cancer prognosis. Unfortunately, a comprehensive and effective framework to measure ITH across cancers is missing. Here, we introduce a scalable measure of chromosomal copy number heterogeneity (CNH) that predicts patient survival across cancers. We show that the level of ITH can be derived from a single-sample copy number profile. Using gene-expression data and live cell imaging we demonstrate that ongoing chromosomal instability underlies the observed heterogeneity. Analysing 11,534 primary cancer samples from 37 different malignancies, we find that copy number heterogeneity can be accurately deduced and predicts cancer survival across tissues of origin and stages of disease. Our results provide a unifying molecular explanation for the different survival rates observed between cancer types.

A Retrospective Study of Noninvasive Prenatal Testing for Chromosome Aneuploidies and Sub-Chromosomal Copy Number Variations in 24359 Single Pregnancies

Background: With the development of whole-genome sequencing, small sub-chromosomal deletions and duplications could be found by non-invasive prenatal testing(NIPT). This study aimed to review the efficiency of NIPT as a screening test for aneuploidies and sub-chromosomal copy number variations (CNVs) in 24359 single pregnancies.Methods: A total of 24359 single pregnancies with different clinical indications were retrospectively analyzed. The positive predictive value （PPV）of chromosome aneuploidies and subchromosomal CNVs were analyzed. Pathogenicity of abnormal NIPT results were assessed according to American College of Medical Genetics and Genomics(ACMG). Results: A total of 442 pregnancies (442/24359,1.9%) were with abnormal NIPT results. PPV for trisomy 21(T21), trisomy 18 (T18), trisomy 13 (T13), and sex chromosome aneuploidies (SCAs) was 84.8%, 54.2%, 11.1% an 40.5% respectively. The PPV for sub-chromosomal CNVs was 59.0% (46/78). The PPV for CNVs ≤5 Mb was 68.9% (31/45), for CNVs within 5-10 Mb was 83.3%(5/6) and for CNVs ≥10 Mb was 37.1% (10/27) respectively. The clinical information, prenatal diagnosis results and follow-up results of 46 true positive cases, 6 cases with sub-chromosomal CNVs inconsistent with NIPT and 1 false negative case were also described in detail.Conclusions: Our data have potential significance in demonstrating the significance of NIPT not only for common whole chromosome aneuploidies but also for sub-chromosomal CNVs. Besides, the clinical information, prenatal diagnosis results and follow-up results of 52 cases with sub-chromosomal CNVs and 1 false negative case would provide important guidance for genetic counseling.