Tatiana Gorodnicheva

Crigler–Najjar syndrome type I, an orphan UTG1A1 enzyme deficiency, manifests at birth with severe unconjugated hyperbilirubinemia. Here we describe sustained clinical response in a pediatric patient with Crigler–Najjar syndrome type I treated with two consecutive doses of AAV8 delivering the UTG1A1 coding sequence. Infusion I (6 × 1012 vg/kg) afforded sustained decrease in serum bilirubin, allowing substantial relaxation of the phototherapy from 12 h to 4 h daily. Infusion II at a double dose was made in 6 months; the decision was intended at complete elimination of phototherapy. However, the elimination led to a sharp increase in bilirubin levels necessitating resumption of phototherapy. The patient is currently stable on 4 h daily phototherapy for 80 weeks since the resumption and 107 weeks since the AAV8 therapy initiation. No toxic side effects were encountered. A slow incremental dynamics in serum bilirubin opens the issue of clinical advisability for subsequent infusions of the drug.

This study evaluates primary template-directed amplification (PTA) for whole exome sequencing (WES) on small fibroblast cell groups, mimicking the limited cell quantities typical of trophectoderm embryo biopsies. PTA’s consistent amplification reduces allelic dropout (ADO) and impoves uniform coverage, overcoming challenges associated with conventional methods such as multiple displacement amplification (MDA). Using fibroblast samples alongside well-characterised genomic references (E701, NA12878), we benchmarked PTA-WES, achieving 97.5% target region coverage at 10x, meeting American College of Medical Genetics and Genomics (ACMG) standards. Preliminary results from embryo biopsies sequenced with PTA-WES showed a median coverage of 102x, significantly improving upon the variability and coverage gaps observed in MDA-WES. The findings support PTA’s potential to enhance the clinical applicability of WES for preimplantation genetic testing for monogenic disorders (PGT-M), expanding capabilities to detect inherited and de novo mutations in embryos. Further optimisation and variant detection analyses are planned to evaluate PTA’s robustness for routine clinical use.