1 / 18

Pulmonary Surfactant Metabolism Dysfunction types 1, 2 and 3

Pulmonary Surfactant Metabolism Dysfunction types 1, 2 and 3. Caroline Archer NE Thames Regional Molecular Genetics 03-Apr-2008. Outline. Clinical overview Physiological Role of the three genes Phenotype of each gene Service need Methodology Results Case studies. 1° Bronchus.

elizabeth-kirk
Download Presentation

Pulmonary Surfactant Metabolism Dysfunction types 1, 2 and 3

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Pulmonary Surfactant Metabolism Dysfunction types 1, 2 and 3 Caroline Archer NE Thames Regional Molecular Genetics 03-Apr-2008

  2. Outline • Clinical overview • Physiological Role of the three genes • Phenotype of each gene • Service need • Methodology • Results • Case studies

  3. 1° Bronchus 2° Bronchus 3° Bronchus Alveoli Bronchiole Alveoli Terminal bronchiole Pulmonary Surfactant Metabolism Dysfunction (SMDP) http://static.howstuffworks.com/gif/adam/images/en/lungs-picture.jpg No surfactant • Decreased pulmonary compliance • Increased tendency for alveoli to collapse

  4. Alveola Alveolar space SMDP Types 1, 2 & 3 by genotype: Diagnosis defined SMDP1 Pulmonary Surfactant protein B (SFTPB) Pulmonary Surfactant protein C (SFTPC) ABCA3 SMDP2 SMDP3

  5. SMDP type 1 Autosomal Recessive mutations SFTPB • 1 per million live births • Term neonates with severe respiratory distress presenting within hours of birth • Refractory to ventilation & synthetic surfactant replacement therapy • Fatal in first three months of life - lung transplant is the only successful intervention • Partial deficiencies may be less severe

  6. SMDP type 2 Autosomal Dominant mutations SFTPC • Incidence unknown • Familial and sporadic (55%) • Highly variable clinical course & severity • Later onset tachypnoea & cyanosis with interstitial lung disease • Rarely acute neonatal lung disease

  7. SMDP type 3 Autosomal Recessive mutations in ABCA3 • Incidence unknown • Phenotypic overlap with SMPD1 and SMDP2 • Severe hypoxic respiratory disease with death in the first three months • Milder paediatric lung disease with survival past infancy • Mutations in ABCA3 modifies phenotype of SMDP2 (SFTPC)

  8. Lung Biopsy • Chest CT • Bronchoalveolar lavage Other investigations • Chest X-ray

  9. Clinical Utility • Supportive care • Consider lung transplantation • No rapid diagnostic test • Genotype critical for parental counselling • Clinical Overlap • Transient symptoms in premature infants respiratory distress syndrome (RDS) • Short term treatment with synthetic surfactant • Proforma • Clinical information required • Clinical queries to an in-house Consultant Intensivist

  10. 2006 Full screen: SFTPB - 10 exons SFTPC - 5 exons ABCA3 - 30 exons • SFTPB linkage – six markers Strategy Considerations • Turnaround Times • Low DNA requirement • Very low referral numbers expected • RNA not possible • Polymorphisms – known susceptibility to RDS • Mutations reported throughout coding region Diagnostic service • 2002 SFTPB ‘common’ mutation service: pick up 0%

  11. Direct Sequencing • 45 exons (all 3 genes) • Robotic PCR set up using 8 span robot • Each gene separate • Touch-down PCR program for all three genes • Direct sequencing using 8 & 96 span robots • Robotic Exosap-IT or Ampure beads • Robotic sequencing set-up • Tailed primers • Robotic clean-up using clean seq beads

  12. Results for Index cases to end 2007 • Overall mutation detection rate 15/33 patients (3/14 patients referred for all 3 genes) • SFTPB: 7/25 • SFTPC: 5/20 • ABCA3: 3/20 • 29 Carrier tests for these index cases • 1 Prenatal diagnosis • 1 Perinatal test • 1 SFTPB Linkage

  13. Still born 38/40 Still born 40/40 Hearing loss & cataracts died 4 weeks Died 4 weeks Alive & Well Miscarriage 10/40 Case Study 1 • Infant with severe respiratory distress • Dependency on ventilation • Consanguineous Asian • SFTPB c.484A>T homozygote (p.Lys162X)

  14. Case Study 2 Child post lung transplant referred for SFTPC • c.215G>A (p.Ser72Asn) heterozygote • No mutation in ABCA3 • Highly conserved cross-species • p.Ile73Thr common mutation

  15. Asian c.127 C>T (p.Arg43Cys) Heterozygote Caucasian c.4747 C>T (p.Arg1583Trp) Heterozygote c. [127 C>T]+[4747 C>T] (p.[Arg1583Trp]+[p.Arg43Cys]) Case Study 3 • Infant with severe respiratory distress and evidence of desquammating interstitial pneumonitis • No mutation detected in SFTPB and SFTPC • ABCA3: Two unclassified variants in trans • Possible origin deamination of C to U • Collaborated on case report for publication

  16. p.Arg1583Trp p.Arg43Cys Tryptophan Cysteine Arginine • Intrans & different physiochemical properties Case Study 3 - Evidence of pathogenicity • Missense change at p.Arg43 previously reported • Location: p.Arg43Cys at the first extracellular loop p.Arg1583Trp near the C-terminus • Highly conserved

  17. Further Work • SFTPC linkage for de novo cases • Use proforma to develop a tiered strategy based on genetic & clinical data. • Now charging for testing - Gene Dossier May 2008 Summary • NE Thames RMG offers screening of SFTPB, SFTPC, ABCA3 for SMDP1, 2 and 3. • This is a group of rare chronic respiratory disorders typically seen in full term neonates and younger children.

  18. Acknowledgements Quen Mok Paediatric Intensive Care Unit Gail Norbury, Lucy Jenkins, Vicky Aldridge, & All Staff NE Thames Regional Molecular Genetics laboratory Great Ormond Street Hospital for Children London WC1N 3JH http://www.ich.ucl.ac.uk/gosh/clinicalservices/Molecular_Genetics Larry Nogee Department of Paediatrics Johns Hopkins University School of Medicine Baltimore USA Sian Jenkins Evelina Children's Hospital St Thomas' Hospital Lambeth Palace Road London SE1 7EH

More Related