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Lab Dept:
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Anatomic Pathology
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Test Name:
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X-LINKED DEAFNESS (POU3F4) KNOWN MUTATION
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General Information
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Lab Order Codes:
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XLIDK
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Synonyms:
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Hearing Loss Genes; POUF4; X-linked deafness with stapes fixation
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CPT Codes:
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83891 x2 – Isolation or extraction of highly purified nucleic acid
83894 x2– Separation by gel electrophoresis
83898 x2 – Amplification of patient nucleic acid, each nucleic acid sequence
83904 x4 – Mutation identification by sequencing, single segment, each segment
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Test Includes:
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Carrier testing for POU3F4 is performed by DHPLC and sequencing.
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Logistics
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Test Indications:
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Testing of a relative for a specific known mutation (carrier testing).
Deafness at the DFN3 locus can be conductive (due to impaired stapes mobility) and/or mixed with a superimposed, often progressive, sensorineural component. Stapedectomy to correct the conductive component is contraindicated because of the possibility of iatrogenic profound hearing loss secondary to a stapes gusher. A stapes gusher occurs because the internal auditory canal is abnormally dilated. The wide communication between the internal auditory canal and inner ear can often be visualized by computerized tomography. The gene, POU3F4, was found to be responsible for this form of X-linked hearing loss by De Kok and colleagues.
The single exon of POU3F4 encodes a transcription factor with a 75 amino acid POU domain and a 63 amino acid homeobox domain. In animal studies, Minowa and colleagues showed Brn4 (POU3F4) deficient mice have profound deafness and inner ear abnormalities. In humans with DFN3, mutations have been found in either of the two binding domains, as well as upstream of POU3F4. In the presence of these large upstream deletions, the coding sequence of POU3F4 can be entirely normal.
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Lab Testing Section:
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Anatomic Pathology - Sendouts
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Referred to:
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University of Iowa, Dr. Richard Smith
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Phone Numbers:
Minneapolis:
Saint Paul:
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612-813-6280
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651-220-6550
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Test Availability:
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Monday – Thursday, 24 hours
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Turnaround Time:
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Approximately 3 months
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Special Instructions:
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Include clinical data, specifically audiograms, CT/MRI reports, and pedigree information. Include name, e-mail, and telephone number of contact person (physician or genetic counselor). Do NOT send on Friday or Saturday.
Please include a completed University of Iowa Request form with the patient of specimen to the laboratory. Informed consent is required.
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Specimen
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Specimen Type:
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Whole blood
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Container:
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Lavender top (EDTA) tube
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Draw Volume:
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10 mL (Minimum 8 mL) blood
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Processed Volume:
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8 – 10 mL whole blood
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Collection:
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Routine venipuncture
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Special Processing:
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Send lavender tubes labeled with a minimum of Name, Date of Birth, and Sex. Include clinical data, specifically audiograms, CT/MRI reports, and pedigree information. Include name, e-mail, and telephone number of contact person (physician or genetic counselor). Mail overnight delivery at Room Temperature Monday - Thursday. Do Not send on Friday or Saturday. Samples may be refrigerated if delivery is delayed.
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Patient Preparation:
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None
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Sample Rejection:
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Specimens older than 48 hours, mislabeled or unlabeled specimens
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Interpretive
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Reference Range:
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No abnormal allele variants detected
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Methodology:
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DHPLC and sequencing
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References:
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Clinical Diagnostics Service, Molecular Otolaryngology Research Lab information sheet from the University of Iowa. June 2010
(319) 335-7997 Fax: (319) 353-5869
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Udates:
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7/29/2010: CPT updates
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