hearing loss & genetics: understanding the basics anna frangulov, b.s. research coordinator...
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Hearing Loss & Genetics:Hearing Loss & Genetics:
Understanding the BasicsUnderstanding the Basics
Anna Frangulov, B.S. Research CoordinatorAnna Frangulov, B.S. Research Coordinator
Children’s Hospital BostonChildren’s Hospital Boston
Why Hearing Loss is Why Hearing Loss is So Common?So Common?
Structure of the EarStructure of the Ear
Sound wave
Inside the Cochlea “snail”
Hair Cells
Nerve
Structure of the EarStructure of the Ear
Conductive HL Sensorineural HL
Genetic
• Infections
• Drug-Related
• Structural
What Causes Hearing Loss?
• Unknown
• Traumas/ Exposures
Non-Genetic
How Genetic HL occurs?How Genetic HL occurs?
Chromosomes in NucleusChromosomes in Nucleus
23 Pairs of Chromosomes
MOM DAD
One Chromosome PairOne Chromosome Pair
Genes“instruction manual”
Genes
Chromosome PairChromosome Pair
Genes
Mutation“error”
How Is Mutation Inherited?How Is Mutation Inherited?
Dominant Dominant ~15%~15% Recessive Recessive ~80%~80% X-Linked X-Linked ~2%~2% Mitochondrial Mitochondrial >2%>2%
Dominant Inheritance Dominant Inheritance
Mutation“error"
CarrierCarrier
Mutation“error"
How a Recessive Mutation is How a Recessive Mutation is Passed?Passed?
Carrier –No Hearing Loss Carrier –No Hearing Loss
Affected Child—Hearing Loss
Recessive Inheritance Recessive Inheritance
If a parent has a dominant mutation, EACH of their children has a 50% chance of having hearing loss
Dominant InheritanceDominant Inheritance Recessive InheritanceRecessive Inheritance
90% of all children w/HL have normal hearing parents!
Parent w/HL Parent w/o HLParent w/o HL
Child w/HL
Child w/ HL
If two parents have a recessivemutation, EACH of their children has a 25% chance of having hearing loss
HOW? WHO? WHY?HOW? WHO? WHY?
HOWHOW
Do We Know If HL is Genetic? Do We Know If HL is Genetic?
WHOWHO Should Have a Genetic Test?Should Have a Genetic Test?
Case A: SyphilisCase A: Syphilis
Case B: CMVCase B: CMV
Case C: PrematurityCase C: Prematurity
Case D: High bilirubin level Case D: High bilirubin level
Everybody with Sensorineural HLEverybody with Sensorineural HL
Also 2 Mutations in Cx26!!Also 2 Mutations in Cx26!!
WHYWHY Should We Have a Genetic Test??Should We Have a Genetic Test??
Benefits for Genetic TestingBenefits for Genetic Testing a definite causea definite cause family members realize that they are family members realize that they are
carriers & determine risk factors for future carriers & determine risk factors for future childrenchildren
helps to find appropriate treatment/ helps to find appropriate treatment/ managementmanagement
Limitations for Genetic TestingLimitations for Genetic Testing does not necessarily find the answer does not necessarily find the answer severity of HL may not be predicted severity of HL may not be predicted a person may have mutations, but not a person may have mutations, but not
have HLhave HL
Things to ConsiderThings to Consider
1.1. Talk to knowledgeable professionalTalk to knowledgeable professional
Primary Care/ Pediatrician
ENT
Audiologist
Clinical GeneticistClinical Geneticist
Genetic CounselorGenetic Counselor
Clinical Molecular GeneticistClinical Molecular Geneticist
Things to ConsiderThings to Consider
2. What tests are done?2. What tests are done?
Cx26Cx26 Cx30Cx30 Mitochondrial TestsMitochondrial Tests PendredPendred
3. Cost3. Cost
UNDERSTANDING UNDERSTANDING TEST RESULTSTEST RESULTS
(example Cx26)(example Cx26)
What Does the Result Mean?What Does the Result Mean?
Two Mutations are FoundTwo Mutations are Found No Mutations are FoundNo Mutations are Found
Mutations w/Unknown Mutations w/Unknown Significance Significance
One Mutation is FoundOne Mutation is Found
??~10%
~70%~18%
~1%
One Mutation FoundOne Mutation Found
Mutation unrelated to deafnessMutation unrelated to deafness Test did not find 2Test did not find 2ndnd mutation mutation Dominant mutationDominant mutation There may be a mutation in another geneThere may be a mutation in another gene
Future in Genetics and HLFuture in Genetics and HL
More Genetic Tests More Genetic Tests
GeneChip TechnologyGeneChip Technology
Research StudiesResearch Studies Connexin 26 Study-Connexin 26 Study- individuals with Cx26 mutations individuals with Cx26 mutations
Genetic Testing and Counseling StudyGenetic Testing and Counseling Study - - If you or your If you or your child has had genetic testing for hearing loss and you child has had genetic testing for hearing loss and you are willing to fill out a questionnaireare willing to fill out a questionnaire
GeneChip Study - GeneChip Study - individuals with hearing loss who and individuals with hearing loss who and parents with normal hearing parents with normal hearing
Novel Gene Discovery StudyNovel Gene Discovery Study - - five or more family five or more family members with hearing loss members with hearing loss
Now also in Spanish!
Educational Material
http://hearing.harvard.edu
Helpful InformationHelpful Information
Genetic Counselor -Genetic Counselor - Rebecca Madore call 617-335-4534 Rebecca Madore call 617-335-4534 to set an appointment or email to set an appointment or email [email protected]@partners.org
Department of Clinical GeneticsDepartment of Clinical Genetics – To make appointment – To make appointment with Clinical Geneticist call 617-355-6394.with Clinical Geneticist call 617-355-6394.
National Society of Genetic Counselors (NSGC)National Society of Genetic Counselors (NSGC) www.nsgc.orgwww.nsgc.org
Research Study Participation & Booklets Orders: Research Study Participation & Booklets Orders: Anna Frangulov Anna Frangulov
617-515-2962 or [email protected] or [email protected]