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  

Gene

Deletion Duplication

Point  Muta/ons  

C G A A G C

T G A A G C

C G A A G C C G A A G C

C G A - G C C G A A G C

A

Gene

Mutation

Nonsense Mutation

Frameshift Mutation

X ……

Gene  Muta/ons  

•  2/3  muta/ons  maternally  inherited  •  1/3  apparently  de  novo    

 (includes  germline  mosaicism)  

Duchenne Becker Deletions ~60-65% ~85%

Duplications 5-10% 5-10%

Small mutations (insertions, deletions, nonsense, splice, etc.)

30-35% 5-10%

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  

Method Target Comment Targeted/familial mutation testing

Tests for small mutation identified in family

•  Requires knowledge of mutation in family

mRNA / cDNA Functional test for rare mutations

•  Requires muscle biopsy

Linkage Tests regions in/near gene (does not test mutation)

• May require 1+ males with DMD • Risk of recombination

Other test options

 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?

JOIN  A  REGISTRY!  What  else  can  I  do?  

Registry  Par/cipa/on  

Why  Join?  

Medical information

Population size

Trial planning

Trial recruitment

Research Advances

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