Forms

Cone-Rod Dystrophy via the CNNM4 Gene

  • Summary and Pricing
  • Clinical Features and Genetics
  • Citations
  • Methods
  • Ordering/Specimens
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TEST METHODS

Sequencing

Test Code Test Copy GenesIndividual Gene PriceCPT Code Copy CPT Codes
2247 CNNM4$780.00 81479 Add to Order
Targeted Testing

For ordering targeted known variants, please proceed to our Targeted Variants landing page.

Turnaround Time

The great majority of tests are completed within 18 days.

Clinical Sensitivity

A CNNM4 mutation analysis in seven ethnically diverse families detected mutations in all Jalili syndrome affected members, and each mutation cosegregated consistently with the disease phenotype. These mutations were not present in 96 control chromosomes (Parry et al. 2009).

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Deletion/Duplication Testing via aCGH

Test Code Test Copy GenesIndividual Gene PriceCPT Code Copy CPT Codes
600 CNNM4$690.00 81479 Add to Order
Pricing Comment

# of Genes Ordered

Total Price

1

$690

2

$730

3

$770

4-10

$840

11-30

$1,290

31-100

$1,670

Over 100

Call for quote

Turnaround Time

The great majority of tests are completed within 28 days.

Clinical Sensitivity

A CNNM4 mutational screening in 7 ethnically diverse families affected by autosomal recessive cone-rod dystrophy and amelogenesis imperfecta identified gross deletions in two families (Parry et al. 2009).

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Clinical Features

Cone-rod dystrophy (CORD/CRD) is a rare hereditary retinal disorder with a worldwide prevalence of ~1 in 40,000. CRD is characterized by dysfunction or degeneration of cone photoreceptors with relative preservation of rod function in the initial stages. The most common symptoms are photophobia and epiphora in bright light, decreased visual acuity, and dyschromatopsia. Fundus changes may vary from mild pigment granularity to a distinct atrophic lesion in the central macula. As the disease progresses, degeneration of rod photoreceptors also occurs and leads to progressive night blindness and peripheral visual field loss (Hamel 2007). Jalili syndrome, which is an autosomal recessive cone-rod dystrophy and amelogenesis imperfecta, is characterized by a combination of photophobia and dental anomalies (Jalili 2010; Parry et al. 2009; Polok et al. 2009).

Genetics

Non syndromic CRD is genetically heterogeneous and exhibits autosomal dominant (ad), autosomal recessive (ar) and, rarely, X-linked (xl) inheritance (Hamel 2007). So far, about 25 genes have been implicated in different forms of CRD (RetNet). One of the ACDP (ancient conserved domain protein) family members CNNM4 (also known as ACDP4) is involved with arCRD. Quantitative PCR studies of the 4 members of ACDP (CNNM1-4) revealed that the CNNM4 is highly expressed in the retina, whereas CNNM1-3 showed markedly higher expression in brain than retina (Parry et al. 2009). CNNM4 and CNNM2 share high amino acid sequence identity (81.4%) and both are implicated in magnesium transport and biomineralization. CNNM4 is predominantly localized in the ganglion cell layers, the inner and outer plexiform layers, and the inner and outer photoreceptor segments of the retina (Parry et al. 2009, de Baaij et al. 2012). Immunostaining of CNNM4 indicates that it is also localized on soma and dendrites of neurons (Guo et al. 2005). These results suggest a possible role of CNNM4 in the maintenance of the ionic content of the extracellular space around the axons, dendrites, synapses in the neural retina and also in tooth enamel formation and in ameloblasts of the developing teeth (Luder et al. 2013; Parry et al. 2009; Guo et al. 2005). CNNM4 is shown to interact with cytochrome oxydase 11 (COX11) to regulate metal ion homeostasis and transport (Guo et al. 2005). Mutations in CNNM4 have been reported to cause CRD and Jalili syndrome due to abnormal ion homeostasis (Polok et al. 2009; Gómez García et al. 2011; Human Gene Mutation Database). Over ten pathogenic variations in CNNM4 have been reported.

Testing Strategy

This test involves bidirectional Sanger sequencing using genomic DNA of all coding exons of the CNNM4 gene plus ~20 bp of flanking non-coding DNA on each side. We will also sequence any single exon (Test #100) or pair of exons (Test #200) in family members of patients with known pathogenic variants or to confirm research results.

Indications for Test

All patients with symptoms suggestive of Cone-rod dystrophy.

Gene

Official Gene Symbol OMIM ID
CNNM4 607805
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT

Disease

Name Inheritance OMIM ID
Jalili Syndrome AR 217080

Related Tests

Name
Amelogenesis Imperfecta Sequencing Panel with CNV Detection
Cone-Rod Dystrophy Sequencing Panel

CONTACTS

Genetic Counselors
Geneticist
Citations
  • de Baaij JHF, Stuiver M, Meij IC, Lainez S, Kopplin K, Venselaar H, Muller D, Bindels RJM, Hoenderop JGJ. 2012. Membrane Topology and Intracellular Processing of Cyclin M2 (CNNM2). J Biol Chem 287: 13644–13655. PubMed ID: 22399287
  • Gómez García I, Oyenarte I, Martínez-Cruz LA. 2011. Purification, crystallization and preliminary crystallographic analysis of the CBS pair of the human metal transporter CNNM4. Acta Crystallographica Section F Structural Biology and Crystallization Communications 67: 349–353. PubMed ID: 21393841
  • Guo D, Ling J, Wang M-H, She J-X, Gu J, Wang C-Y. 2005. Physical interaction and functional coupling between ACDP4 and the intracellular ion chaperone COX11, an implication of the role of ACDP4 in essential metal ion transport and homeostasis. Mol. Pain 1: 15. PubMed ID: 15840172
  • Hamel CP. 2007. Cone rod dystrophies. Orphanet J Rare Dis 1;2:7. PubMed ID: 17270046
  • Human Gene Mutation Database (Bio-base).
  • Jalili IK. 2010. Cone-rod dystrophy and amelogenesis imperfecta (Jalili syndrome): phenotypes and environs. Eye 24: 1659–1668. PubMed ID: 20706282
  • Luder HU, Gerth-Kahlert C, Ostertag-Benzinger S, Schorderet DF. 2013. Dental Phenotype in Jalili Syndrome Due to a c.1312 dupC Homozygous Mutation in the CNNM4 Gene. PLoS ONE 8: e78529. PubMed ID: 24194943
  • Parry DA, Mighell AJ, El-Sayed W, Shore RC, Jalili IK, Dollfus H, Bloch-Zupan A, Carlos R, Carr IM, Downey LM, Blain KM, Mansfield DC, et al. 2009. Mutations in CNNM4 Cause Jalili Syndrome, Consisting of Autosomal-Recessive Cone-Rod Dystrophy and Amelogenesis Imperfecta. Am J Hum Genet 84: 266–273. PubMed ID: 19200525
  • Parry DA, Mighell AJ, El-Sayed W, Shore RC, Jalili IK, Dollfus H, Bloch-Zupan A, Carlos R, Carr IM, Downey LM, Blain KM, Mansfield DC, et al. 2009. Mutations in CNNM4 Cause Jalili Syndrome, Consisting of Autosomal-Recessive Cone-Rod Dystrophy and Amelogenesis Imperfecta. The American Journal of Human Genetics 84: 266–273.
  • Polok B, Escher P, Ambresin A, Chouery E, Bolay S, Meunier I, Nan F, Hamel C, Munier FL, Thilo B, Mégarbané A, Schorderet DF. 2009. Mutations in CNNM4 Cause Recessive Cone-Rod Dystrophy with Amelogenesis Imperfecta. The American Journal of Human Genetics 84: 259–265. PubMed ID: 19200527
  • RetNet: Genes and Mapped Loci Causing Retinal Diseases
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TEST METHODS

Bi-Directional Sanger Sequencing

Test Procedure

Nomenclature for sequence variants was from the Human Genome Variation Society (http://www.hgvs.org).  As required, DNA is extracted from the patient specimen.  PCR is used to amplify the indicated exons plus additional flanking non-coding sequence.  After cleaning of the PCR products, cycle sequencing is carried out using the ABI Big Dye Terminator v.3.0 kit.  Products are resolved by electrophoresis on an ABI 3730xl capillary sequencer.  In most cases, sequencing is performed in both forward and reverse directions; in some cases, sequencing is performed twice in either the forward or reverse directions.  In nearly all cases, the full coding region of each exon as well as 20 bases of non-coding DNA flanking the exon are sequenced.

Analytical Validity

As of March 2016, we compared 17.37 Mb of Sanger DNA sequence generated at PreventionGenetics to NextGen sequence generated in other labs. We detected only 4 errors in our Sanger sequences, and these were all due to allele dropout during PCR. For Proficiency Testing, both external and internal, in the 12 years of our lab operation we have Sanger sequenced roughly 8,800 PCR amplicons. Only one error has been identified, and this was due to sequence analysis error.

Our Sanger sequencing is capable of detecting virtually all nucleotide substitutions within the PCR amplicons. Similarly, we detect essentially all heterozygous or homozygous deletions within the amplicons. Homozygous deletions which overlap one or more PCR primer annealing sites are detectable as PCR failure. Heterozygous deletions which overlap one or more PCR primer annealing sites are usually not detected (see Analytical Limitations). All heterozygous insertions within the amplicons up to about 100 nucleotides in length appear to be detectable. Larger heterozygous insertions may not be detected. All homozygous insertions within the amplicons up to about 300 nucleotides in length appear to be detectable. Larger homozygous insertions may masquerade as homozygous deletions (PCR failure).

Analytical Limitations

In exons where our sequencing did not reveal any variation between the two alleles, we cannot be certain that we were able to PCR amplify both of the patient’s alleles. Occasionally, a patient may carry an allele which does not amplify, due for example to a deletion or a large insertion. In these cases, the report contains no information about the second allele.

Similarly, our sequencing tests have almost no power to detect duplications, triplications, etc. of the gene sequences.

In most cases, only the indicated exons and roughly 20 bp of flanking non-coding sequence on each side are analyzed. Test reports contain little or no information about other portions of the gene, including many regulatory regions.

In nearly all cases, we are unable to determine the phase of sequence variants. In particular, when we find two likely causative mutations for recessive disorders, we cannot be certain that the mutations are on different alleles.

Our ability to detect minor sequence variants, due for example to somatic mosaicism is limited. Sequence variants that are present in less than 50% of the patient’s nucleated cells may not be detected.

Runs of mononucleotide repeats (eg (A)n or (T)n) with n >8 in the reference sequence are generally not analyzed because of strand slippage during PCR and cycle sequencing.

Unless otherwise indicated, the sequence data that we report are based on DNA isolated from a specific tissue (usually leukocytes). Test reports contain no information about gene sequences in other tissues.

Deletion/Duplication Testing Via Array Comparative Genomic Hybridization

Test Procedure

Equal amounts of genomic DNA from the patient and a gender matched reference sample are amplified and labeled with Cy3 and Cy5 dyes, respectively. To prevent any sample cross contamination, a unique sample tracking control is added into each patient sample. Each labeled patient product is then purified, quantified, and combined with the same amount of reference product. The combined sample is loaded onto the designed array and hybridized for at least 22-42 hours at 65°C. Arrays are then washed and scanned immediately with 2.5 µM resolution. Only data for the gene(s) of interest for each patient are extracted and analyzed.

Analytical Validity

PreventionGenetics' high density gene-centric custom designed aCGH enables the detection of relatively small deletions and duplications within a single exon of a given gene or deletions and duplications encompassing the entire gene. PreventionGenetics has established and verified this test's accuracy and precision.

Analytical Limitations

Our dense probe coverage may allow detection of deletions/duplications down to 100 bp; however due to limitations and probe spacing this cannot be guaranteed across all exons of all genes. Therefore, some copy number changes smaller than 100-300 bp within a targeted large exon may not be detected by our array.

This array may not detect deletions and duplications present at low levels of mosaicism or those present in genes that have pseudogene copies or repeats elsewhere in the genome.

aCGH will not detect balanced translocations, inversions, or point mutations that may be responsible for the clinical phenotype.

Breakpoints, if occurring outside the targeted gene, may be hard to define.

The sensitivity of this assay may be reduced when DNA is extracted by an outside laboratory.

Order Kits

Ordering Options


myPrevent - Online Ordering
  • The test can be added to your online orders in the Summary and Pricing section.
  • Once the test has been added log in to myPrevent to fill out an online requisition form.
REQUISITION FORM
  • A completed requisition form must accompany all specimens.
  • Billing information along with specimen and shipping instructions are within the requisition form.
  • All testing must be ordered by a qualified healthcare provider.

SPECIMEN TYPES
WHOLE BLOOD

(Delivery accepted Monday - Saturday)

  • Collect 3 ml -5 ml (5 ml preferred) of whole blood in EDTA (purple top tube) or ACD (yellow top tube). For Test #500-DNA Banking only, collect 10 ml -20 ml of whole blood.
  • For small babies, we require a minimum of 1 ml of blood.
  • Only one blood tube is required for multiple tests.
  • Ship blood tubes at room temperature in an insulated container. Do not freeze blood.
  • During hot weather, include a frozen ice pack in the shipping container. Place a paper towel or other thin material between the ice pack and the blood tube.
  • In cold weather, include an unfrozen ice pack in the shipping container as insulation.
  • At room temperature, blood specimen is stable for up to 48 hours.
  • If refrigerated, blood specimen is stable for up to one week.
  • Label the tube with the patient name, date of birth and/or ID number.

DNA

(Delivery accepted Monday - Saturday)

  • Send in screw cap tube at least 5 µg -10 µg of purified DNA at a concentration of at least 20 µg/ml for NGS and Sanger tests and at least 5 µg of purified DNA at a concentration of at least 100 µg/ml for gene-centric aCGH, MLPA, and CMA tests, minimum 2 µg for limited specimens.
  • For requests requiring more than one test, send an additional 5 µg DNA per test ordered when possible.
  • DNA may be shipped at room temperature.
  • Label the tube with the composition of the solute, DNA concentration as well as the patient’s name, date of birth, and/or ID number.
  • We only accept genomic DNA for testing. We do NOT accept products of whole genome amplification reactions or other amplification reactions.

CELL CULTURE

(Delivery preferred Monday - Thursday)

  • PreventionGenetics should be notified in advance of arrival of a cell culture.
  • Culture and send at least two T25 flasks of confluent cells.
  • Some panels may require additional flasks (dependent on size of genes, amount of Sanger sequencing required, etc.). Multiple test requests may also require additional flasks. Please contact us for details.
  • Send specimens in insulated, shatterproof container overnight.
  • Cell cultures may be shipped at room temperature or refrigerated.
  • Label the flasks with the patient name, date of birth, and/or ID number.
  • We strongly recommend maintaining a local back-up culture. We do not culture cells.
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