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The study employs the fluorescence in situ hybridization (FISH) mapping technique to analyze the de novo, apparently the balanced chromosome rearrangements (ABCR) for determining the various characteristics that leads to phenotypic abnormality in humans.

The MIC 11 antigen is expressed on human cells and is characterized by reaction with a monoclonal antibody (mAb), 16.3A5. The gene controlling MIC 11 was recently mapped to the p13 region of chromosome 11 within 500 kb of the gene encoding CD59, a complement regulatory protein. The present report investigates the antigenic relationship between these cell-membrane determinants and sets out evidence that MIC 11 and CD59 are encoded by the same gene. Western blotting of human erythrocyte membrane proteins and purified membrane CD59 showed that 16.3A5 anti-MIC 11 antibody bound to a 19-24 000 MW band with the characteristic appearance of CD59 protein, and gave staining patterns identical to those obtained with the CD59 antibody, BRIC 229. The binding of 16.3A5 monoclonal lgG to purified urine-derived CD59 in enzyme-linked immunosorbent assay (ELISA) was inhibited by YTH 53.1 rat CD59 antibody, indicating that the MIC 11 epitope is the same as, or close to, that recognized by CD59 antibodies such as YTH 53.1, BRIC 229 and 2/24. Prior exposure of erythrocytes to 16.3A5 anti-MIC 11 also reduced the ability of the CD59 antibodies, BRIC 229 and YTH 53.1, to block the complement-inhibiting function of membrane CD59. Anti-MIC 11 antibody alone, however, had no inhibitory effect on CD59 function. This may be due to its relatively low binding affinity or to some slight difference in epitope specificity. Further studies using immunofluorescence showed that the MIC 11 epitope, like CD59, is absent from EBV-B cells lacking GP1-anchored proteins and from a B cell line specifically deficient in CD59 protein. Overall, the results provide strong evidence that MIC 11 is a determinant on the CD59 molecule. [ABSTRACT FROM AUTHOR]

The aetiology of microphthalmia is poorly understood but it is likely that both environmental and genetic mechanisms are involved. Recently interest has focussed on polygenic inheritance as an explanation for variable expressivity of a number of genetic disorders. We present a family with a combination of NF1 and PAX6 mutation where microphthalmia was identified and we suggest that this is due to the two genes acting either additively or synergistically. Case 1 was noted at birth to have a small right eye and a fixed dilated left pupil. Ophthalmological examination revealed significant microphthalmos of the right eye. The left eye was of normal size but had an absent iris sphincter. Her mother had neurofibromatosis 1 (NF1) and her father had Leber's amaurosis. Over the first year of life she developed multiple cafe au lait macules and axilliary freckling. Case 2 is the mother of case 1. Manifestations of NF1 included cafe au lait macules, neurofibromas, spinal tumour, optic glioma and cataracts. Ophthalmological examination of KJs eyes demonstrated bilateral reduction in corneal diameter, iris stromal hypoplasia and foveal hypoplasia. DNA sequencing of the PAX6 gene revealing a cytosine to thiamine transition in exon 5 of the gene causing a missense mutation (R38W). It is clear that both RJ and KJ carry mutations in PAX6 and NF1. Microphthalmia is not commonly associated PAX6 or NF1 mutations and it is hypothesised that the two mutations combine to produce the observed phenotype. [ABSTRACT FROM AUTHOR]

Background: Classic aniridia is a highly penetrant autosomal dominant disorder characterised by congenital absence of the iris, foveal hypoplasia, optic disc anomalies and progressive opacification of the cornea. >90% of cases of classic aniridia are caused by heterozygous, loss-of-function variants affecting the PAX6 locus., Methods: Short-read whole genome sequencing was performed on 51 (39 affected) individuals from 37 different families who had screened negative for mutations in the PAX6 coding region., Results: Likely causative mutations were identified in 22 out of 37 (59%) families. In 19 out of 22 families, the causative genomic changes have an interpretable deleterious impact on the PAX6 locus. Of these 19 families, 1 has a novel heterozygous PAX6 frameshift variant missed on previous screens, 4 have single nucleotide variants (SNVs) (one novel) affecting essential splice sites of PAX6 5' non-coding exons and 2 have deep intronic SNV (one novel) resulting in gain of a donor splice site. In 12 out of 19, the causative variants are large-scale structural variants; 5 have partial or whole gene deletions of PAX6 , 3 have deletions encompassing critical PAX6 cis -regulatory elements, 2 have balanced inversions with disruptive breakpoints within the PAX6 locus and 2 have complex rearrangements disrupting PAX6 . The remaining 3 of 22 families have deletions encompassing FOXC1 (a known cause of atypical aniridia). Seven of the causative variants occurred de novo and one cosegregated with familial aniridia. We were unable to establish inheritance status in the remaining probands. No plausibly causative SNVs were identified in PAX6 cis -regulatory elements., Conclusion: Whole genome sequencing proves to be an effective diagnostic test in most individuals with previously unexplained aniridia., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY. Published by BMJ.)

Identifying causative variants in cis-regulatory elements (CRE) in neurodevelopmental disorders has proven challenging. We have used in vivo functional analyses to categorize rigorously filtered CRE variants in a clinical cohort that is plausibly enriched for causative CRE mutations: 48 unrelated males with a family history consistent with X-linked intellectual disability (XLID) in whom no detectable cause could be identified in the coding regions of the X chromosome (chrX). Targeted sequencing of all chrX CRE identified six rare variants in five affected individuals that altered conserved bases in CRE targeting known XLID genes and segregated appropriately in families. Two of these variants, FMR1CRE and TENM1CRE, showed consistent site- and stage-specific differences of enhancer function in the developing zebrafish brain using dual-color fluorescent reporter assay. Mouse models were created for both variants. In male mice Fmr1CRE induced alterations in neurodevelopmental Fmr1 expression, olfactory behavior and neurophysiological indicators of FMRP function. The absence of another likely causative variant on whole genome sequencing further supported FMR1CRE as the likely basis of the XLID in this family. Tenm1CRE mice showed no phenotypic anomalies. Following the release of gnomAD 2.1, reanalysis showed that TENM1CRE exceeded the maximum plausible population frequency of a XLID causative allele. Assigning causative status to any ultra-rare CRE variant remains problematic and requires disease-relevant in vivo functional data from multiple sources. The sequential and bespoke nature of such analyses renders them time-consuming and challenging to scale for routine clinical use., Competing Interests: No authors have competing interests