Application of multi-omic approaches to investigate novel LZTR1 gene variants and identify therapeutic targets implicated in the pathogenesis of noonan syndrome (NS)

Maharaj Avinaash Vickram; Sumana Chatterjee; Miho Ishida; Bertola Debora R.; Agwu Juliana Chizo; Carles Gaston-Massuet; McGuffin Liam J.; Storr Helen L.

doi:10.1530/endoabs.111.OC10.1

OC10.1

Prev Next

Section Contents Cite

Endocrine Abstracts (2025) 111 OC10.1 | DOI: 10.1530/endoabs.111.OC10.1

BSPED2025 Oral Communications Endocrine Oral Communications 4 (8 abstracts)

Application of multi-omic approaches to investigate novel LZTR1 gene variants and identify therapeutic targets implicated in the pathogenesis of noonan syndrome (NS)

Avinaash Vickram Maharaj ¹ , Sumana Chatterjee ¹ , Miho Ishida ¹ , Débora R. Bertola ² , Juliana Chizo Agwu ³ , Carles Gaston-Massuet ¹ , Liam J. McGuffin ⁴ & Helen L. Storr ¹

Author affiliations

¹Centre for Endocrinology, William Harvey Research Institute, QMUL, London, United Kingdom; ²Department of Paediatrics, University of São Paulo, São Paulo, Brazil; ³Institute of Clinical Sciences, College of Medicine and Dental Sciences, University of Birmingham, Birmingham, United Kingdom; ⁴School of Biological Sciences, University of Reading, Reading, United Kingdom

Introduction: Noonan syndrome (NS) is caused by genetic variations which alter the RAS-MAPK pathway leading to hyperactivation of signalling. However, the pathogenesis of multisystem disease including short stature, is poorly understood. NS-affiliated missense LZTR1 variants have been associated with defective ubiquitination of Ras leading to increased Ras substrate availability. We hypothesised that Ras dysregulation may attenuate p53 signalling and investigated the role of LZTR1 in this pathway.

Methods: Two patients with short stature and NS underwent whole exome sequencing revealing the presence of dominantly inherited LZTR1 variants. Both single nucleotide substitutions were generated by mutagenesis of an N-terminal MYC tagged-LZTR1-cDNA. Constructs were expressed in mammalian cells and lysates prepared for phosphoproteomics. Analysis of transcriptomic data was conducted using Ingenuity Pathway-Analysis. Significant phospho-peptides, protein-protein interactions and pathways of interest were probed using immunoblotting, immunofluorescence, nanoluciferase assays and in-silico modelling.

Results: Both heterozygous LZTR1 variants were shown in-vitro to be thermodynamically stable and associated with elevated pan-Ras levels. Phosphoproteomics revealed upregulation of the histone acetyltransferase inhibitor, NOC2L, in both variants. This finding, consistent upon immunoblotting and immunofluorescence, was associated with impaired p53 acetylation. Effectors of the DNA damage response (DDR), ATM and CHK1 appeared enhanced in both LZTR1 variants whilst two major substrates representative of their kinase activity, Rad50 and Adducin (ADD1/2), were preferentially phosphorylated, via residues Serine 635 and Serine 713/726 respectively. Despite apparent activation of the DDR and diminished p53 activity, levels of LC3 and phosphorylated-p70-S6-kinase were increased. In-silico structure modelling and nanoluciferase assays suggested that LZTR1 interacts with NOC2L, an interaction previously unknown and disrupted in both LZTR1 variants.

Conclusion: NOC2L and p53 form a complex which dictates p53 activation. We demonstrate a novel interaction between NOC2L and LZTR1 and hypothesise that LZTR1 modulates activity of this complex. NOC2L upregulation leads to p53-mediated transcription inhibition. LZTR1 mutations potentiate NOC2L activity leading to reduced apoptosis and compensatory increases in autophagy that perpetuate chronic DNA damage gaining insights into NS pathogenesis. Currently, no inhibitors of NOC2L exist, but this complex represents a therapeutic target that warrants exploration. Future work will ascertain the role of NOC2L in other genetic causes of NS.