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Bardet-Biedl Syndrome via the BBS1 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
252 BBS1$890.00 81406 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
Mutations in the BBS1 gene are the most frequent cause of BBS. BBS1 mutations are estimated to cause approximately ~23% of BBS cases (Mykytyn et al. 2003; Katsanis 2004).

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Deletion/Duplication Testing via aCGH

Test Code Test Copy GenesIndividual Gene PriceCPT Code Copy CPT Codes
600 BBS1$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 Features
The BBS1 gene encodes the BBS1 protein, which is found in the centromes of mitotically dividing cells and in the basal bodies of the primary cilia (Kulaga et al. 2004). BBS1 interacts with six other BBS proteins (BBS2, BBS4, BBS5, BBS7, BBS9 and BBS11) to form a higher order structure known as the BBSome; the BBSome is critical for the maintenance and function of the primary cilia (Nachury et al. 2007). Recessive mutations in BBS1 lead to defects primary cilia and symptoms of Bardet-Biedl Syndrome (BBS).  A mix of missense, nonsense, frameshift and splicing mutations has been reported in the BBS1 gene. The M390R missense mutation is the most common causative mutation (Mykytyn et al. 2002; Mykytyn et al. 2003).
Genetics
Bardet-Biedl Syndrome (BBS) is an autosomal recessive disorder marked by primary features of obesity, polydactyly, pigmentary retinopathy, hypogonadism, renal anomalies and mental retardation (Elbedour et al. 1994; Sheffield. 2010). Secondary features include diabetes, hypertension and congenital heart defects (Green et al. 1989). Although BBS is a rare condition, diagnosis is complicated by the fact that many of the clinical features (i.e. obesity, diabetes, hypertension and developmental delay) are common. In addition, many of the BBS clinical features overlap with those of other well-described developmental disorders, including Meckel-Gruber Syndrome (MKS), Joubert Syndrome (JBTS), Nephronophthisis (NPH), Senior-Loken Syndrome (SLS), Leber Congenital Amaurosis (LCA) and Alstrom Syndrome.
Testing Strategy
The Bi-Directional Sanger Sequencing test interrogates all 17 coding exons (1-17) of the BBS1 gene, plus ~20 bp of flanking non-coding DNA on either side of each exon. We will also sequence any single exon (Test #100) or pair of exons (Test #200) in family members of patients with known mutations or to confirm research results. Please note, the Sanger sequencing test is only designed to detect DNA substitutions (i.e. missense, nonsense, splicing mutations) and small insertions and/or deletions (i.e. frameshift and splice-site mutations).  For large deletions spanning one or more exons, please see our gene-centric array CGH test (#600).
Indications for Test
Candidates for this test are patients with symptoms consistent with BBS and family members of patients who have known BBS1 mutations. Conclusive connections between clinical features and individual mutated BBS genes have not yet been made.

Gene

Official Gene Symbol OMIM ID
BBS1 209901
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT

Disease

Name Inheritance OMIM ID
Bardet-Biedl Syndrome 1 209900

Related Tests

Name
Bardet-Biedl Syndrome Sequencing Panel
Bardet-Biedl Syndrome via the ARL6/BBS3 Gene
Bardet-Biedl Syndrome via the BBS10 Gene
Bardet-Biedl Syndrome via the BBS12 Gene
Bardet-Biedl Syndrome via the BBS2 Gene
Bardet-Biedl Syndrome via the BBS4 Gene
Bardet-Biedl Syndrome via the BBS5 Gene
Bardet-Biedl Syndrome via the BBS7 Gene
Bardet-Biedl Syndrome via the BBS9 Gene
Bardet-Biedl Syndrome via the MKKS/BBS6 Gene
Bardet-Biedl Syndrome via the TRIM32/BBS11 Gene
Bardet-Biedl Syndrome via the TTC8/BBS8 Gene
Joubert and Meckel-Gruber Syndromes via the CEP290 Gene
Joubert Syndrome, Meckel-Gruber Syndrome, and Nephronophthisis via the TMEM67 Gene
Meckel-Gruber Syndrome via the MKS1 Gene
Nephronophthisis / Senior-Loken Syndrome and Bardet-Biedl Syndrome via the SDCCAG8 Gene

CONTACTS

Genetic Counselors
Geneticist
Citations
  • Elbedour K, Zucker N, Zalzstein E, Barki Y, Carmi R. 1994. Cardiac abnormalities in the Bardet-Biedl syndrome: echocardiographic studies of 22 patients. Am. J. Med. Genet. 52: 164–169. PubMed ID: 7802002
  • Green JS, Parfrey PS, Harnett JD, Farid NR, Cramer BC, Johnson G, Heath O, McManamon PJ, O’Leary E, Pryse-Phillips W. 1989. The cardinal manifestations of Bardet–Biedl syndrome, a form of Laurence–Moon–Biedl syndrome. New England Journal of Medicine 321: 1002–1009. PubMed ID: 2779627
  • Katsanis N. 2004. The oligogenic properties of Bardet-Biedl syndrome. Human Molecular Genetics 13: 65R–71. PubMed ID: 14976158
  • Kulaga HM, Leitch CC, Eichers ER, Badano JL, Lesemann A, Hoskins BE, Lupski JR, Beales PL, Reed RR, Katsanis N. 2004. Loss of BBS proteins causes anosmia in humans and defects in olfactory cilia structure and function in the mouse. Nature Genetics 36: 994–998. PubMed ID: 15322545
  • Mykytyn K, Nishimura DY, Searby CC, Beck G, Bugge K, Haines HL, Cornier AS, Cox GF, Fulton AB, Carmi R. 2003. Evaluation of Complex Inheritance Involving the Most Common Bardet-Biedl Syndrome Locus (BBS1). The American Journal of Human Genetics 72: 429–437. PubMed ID: 12524598
  • Mykytyn K, Nishimura DY, Searby CC, Shastri M, Yen H, Beck JS, Braun T, Streb LM, Cornier AS, Cox GF, Fulton AB, Carmi R, et al. 2002. Identification of the gene (BBS1) most commonly involved in Bardet-Biedl syndrome, a complex human obesity syndrome. Nature Genetics 31: 435-438. PubMed ID: 12118255
  • Nachury MV, Loktev AV, Zhang Q, Westlake CJ, Peränen J, Merdes A, Slusarski DC, Scheller RH, Bazan JF, Sheffield VC, Jackson PK. 2007. A Core Complex of BBS Proteins Cooperates with the GTPase Rab8 to Promote Ciliary Membrane Biogenesis. Cell 129: 1201–1213. PubMed ID: 17574030
  • Sheffield, V.C. 2010. The blind leading the obese: the molecular pathophysiology of a human obesity syndrome. Trans Am Clin Climatol Assoc 121:172-182. PubMed ID: 20697559
Order Kits
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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