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A Mosaic Activating Mutation in AKT1 Associated With The Proteus Syndrome Lindhurst, et al.

A Mosaic Activating Mutation in AKT1 Associated With The Proteus Syndrome Lindhurst, et al. Jake Bowling. Proteus Syndrome. Joseph Merrick- Elephant Man Characterized by patchy/segmental overgrowth & hyperplasia of multiple tissues, notably skin, and high susceptibility to tumors.

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A Mosaic Activating Mutation in AKT1 Associated With The Proteus Syndrome Lindhurst, et al.

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  1. A Mosaic Activating Mutation in AKT1 Associated With The Proteus SyndromeLindhurst, et al. Jake Bowling

  2. Proteus Syndrome • Joseph Merrick- Elephant Man • Characterized by patchy/segmental overgrowth & hyperplasia of multiple tissues, notably skin, and high susceptibility to tumors. • <1 in a million

  3. Evidence For Mosaicism • Has never been reported to recur in a family • Has been reported in discordant twins • Wide variety of severities • ~20 years

  4. Hypothesis • Proteus is caused by a somatic mutation that is lethal when constitutive, resulting in a mosaic disorder. • Earlier mutation = more severe disease • Approach- Sequence genomes of affected tissues, searching for common mutations

  5. Initial Sequencing • 4 tissue labels- “affected”, “unaffected”, “unknown” and control. • 11 cutaneous biopsies from 6 Proteus patients (7 affected, 4 unaffected) • Found over 200,000 variants compared to human reference sequence • Only one was significant (present in 3.6-51% of reads) - AKT1G>A , predicting a substitution of lysine for glutamine at amino acid 17 (missense). • AKT1 codes for a protein kinase, part of a signaling pathway.

  6. Validation • Assay using restriction enzyme digestion (E. coli), PCR, electropherography. • Mutation negative in all 27 controls tested. • 97 affected samples from 29 Proteus patients- 75 mutation positive (p-value <.001) • 26 of 29 patients mutation positive (only 6 reads from the 3)

  7. A) Shows enzyme restriction methodology inc. forward & reverse primers, endonuclease site. • C) Shows prevalence of mutant allele in the 29 patients (ranges 1% to 47%)

  8. Functionality • Western Blot used antibodies specific to phosphorylation at Ser473 and Thr308 • Cells grown serum-free show higher phosphorylation (activation) in mutant cells than wild-type cells (p-value <.005). • Bottom Line: Mutation causes activation / upregulation. • PI3K-AKT-mTOR pathway- large signaling pathway, overactivation limits apoptosis.

  9. Conclusions • Definitive- This mutation causes Proteus • Not exclusive • 2 of 38 proteus blood smears mutation positive- supports mutation being detrimental to hematopoeisis and makes diagnosis with blood challenging. • Mice data supports

  10. Cancer • Catalogue of Somatic Mutations in Cancer database • 116 of 7942 samples contained mutation (breast, thyroid, urinary, lung, endometrial) • AKT upregulation - tumor susceptibility

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