Back to the Basics: Gene/c Tes/ng & Registries PPMD Connect Conference June 2010 Vanessa Rangel Miller, MS, CGC coordinator@duchenneconnect.org
Overview • • • • •
Gene/cs &Tes/ng Benefit & Limita/ons Tes/ng Pathway Family Scenarios Registry Par/cipa/on
GENETICS & INHERITANCE
Gene/cs – Xp21.2 – Largest gene in human body – Spans ~2.2 MB or ~0.1% of genome – cDNA transcript is ~14kb – 79 exons (0.6% of gene) – Large introns cons/tute 99.4% of gene – 8 promoters
DMD
Genes
www.gene/cs.au.edu
exon
Dele/ons/Duplica/ons Â
Gene
Deletion
Duplication
Point Muta/ons Gene C
G
A
A
G
C Mutation
T
C
G
A
A
G
C
C
C
G
A
-
G
C
C
A
G
G
A
A
A
A
G
C
G
C
G
A
Frameshift Mutation
A
G
C
X …… Nonsense Mutation
Gene Muta/ons Duchenne
Becker
~60-65%
~85%
Duplications
5-10%
5-10%
Small mutations (insertions, deletions, nonsense, splice, etc.)
30-35%
5-10%
Deletions
• 2/3 muta/ons maternally inherited • 1/3 apparently de novo (includes germline mosaicism)
Gene/c Counseling X-‐linked inheritance – 2/3 carriers • • • •
1 in 4 affected male 1 in 4 normal male 1 in 4 carrier female 1 in 4 non-‐carrier female
– 1/3 non-‐carriers • ~15-‐20% recurrence in future pregnancies • Maternal and paternal origin reported
• Review family history with care provider • Aids medical management • Contributes to tes/ng of addi/onal rela/ves
GENETIC TESTING
Benefits & Limita/ons • Confirms the clinical diagnosis • Minimal procedure risk • Family members – Improve risk assessment – Diagnosis, reassurance
• Research studies & clinical trials
May require mul/ple tests May not iden/fy a muta/on Unexpected results May not indicate prognosis/ severity • Cost & /me for results • • • •
What should I ask? • How can my child be tested? – Blood sample – Medical care provider
• How does my provider order tes/ng?
• What should I know before the test is ordered? – – – – – – –
Method Detec/on Cost Insurance & Billing Turnaround /me Possible results Next steps
Gene/c Test Pathway Following Clinical Exam and CK: Step 1 – Test for Exon Deletions/Duplications MLPA - Exon deletions & duplications Dystrophin Array CGH - Exon deletions & duplications Quantitative PCR - Exon deletions & duplications Multiplex PCR – Specific exon deletions Southern - Exon deletions & some duplications
Gene/c Tes/ng Pathway Step 2 Test for Point Mutations Sequence Analysis - Determines sequence for coding region Mutation Scanning (DDGE, SSCP, DHPLC) - Scans coding region for potential sequence changes - Followed by sequencing to identify the specific change SCAIP - Combines testing for large & small deletions, point mutations - Separate test for duplications
Gene/c Tes/ng Pathway Other test options Method
Target
Comment
Targeted/familial mutation testing
Tests for small mutation identified in family Functional test for rare mutations
• Requires knowledge of mutation in family
Tests regions in/near gene (does not test mutation)
• May require 1+ males with DMD • Risk of recombination
mRNA / cDNA Linkage
• Requires muscle biopsy
Reading the Results • Your doctor may interpret your results • What does it mean if a muta/on is found • Muta/on not found • Variant? • What your results will not tell you • Prognosis • Variability • How to use results in a meaningful way for your family • Compare with your family tree
FAMILY TESTING
Family Member Tes/ng • A del/dup is known in the family – Use method reliable to iden/fy the muta/on
• A small/point muta/on is known in family – Targeted sequence analysis
• No muta/on known – Follow comprehensive test pathway
• Defer asymptoma/c carrier tes/ng in minors
Family Scenarios – Carrier Tes/ng • Family history – Obligate carrier females – Females with no family history • Carrier • Germline mosaicism • De novo muta/on
– Sisters may be at risk to be carriers • Offer carrier tes/ng & gene/c counseling
• Carrier/confirma/on tes/ng – Aid medical management – Contributes to tes/ng of addi/onal rela/ves
What do I do? Ask for a copy of your test results! Ques/ons to discuss with your doctor: – I had a muscle biopsy, do I need gene/c tes/ng? – No muta/on was found, do I need more tes/ng? – Par/cipated research tes/ng, do I need other tes/ng? – Had tes/ng in the past, should I be re-‐tested?
Who else can help?
What else can I do?
JOIN A REGISTRY!
Registry Par/cipa/on
Why  Join?  Trial recruitment
Medical information
Research Advances
Population size
Trial planning
Learn from others
Community interest
I’m registered, now what? • Explore the site, learn from others • Keep your account up-‐to-‐date – Send in your test results
• Watch for emails • Encourage others to join – Help advance research & future treatment for the community
Summary • • • •
What to consider before gene/c tes/ng Comprehensive test pathway What results mean for you and your family Future medical therapies
• Registry Par/cipa/on is IMPORTANT – Beoer understand the associa/ons between genes & disease
Acknowledgements PPMD
Pat Furlong Holly Peay Kim Galbraith Ryan Fischer Brian Denger
Innolyst, Inc. Kyle Brown
Emory University
Yetsa Adadevoh Andy Fauceo Ken Loud Pat Olney Madhuri Hegde
DuchenneConnect advisors Our parJcipants & families