CNGB1

cGMP stands for cyclic guanosine monophosphate (cGMP) which is a cyclic nucleotide derived from guanosine triphosphate (GTP). Cyclic nucleotide-gated (CNG) ion channels are activated by binding cGMP or cAMP (cyclic adenosine monophosphate). Changes in intracellular concentrations of cyclic nucleotides are transduced into changes in membrane potential and calcium ion (Ca2+) concentration. In the retinal rod photoreceptor cGMP-gated cation channel, the CNGB1 gene codes for the beta subunit and the CNGA1 gene codes for the alpha subunit.

Amino acid changes for missense mutations:

In olfactory receptor neurons CNG channels generate a receptor current in response to an odorant-induced rise in cAMP. This channel is comprised of CNGA2 which is the principal subunit plus two modulatory subunits, CNGA4 and CNGB1b. CNGB1 -/- deficient mice show decreased olfactory performance and electro-olfactogram responses show a reduced amplitude and decelerated onset and recovery kinetics compared with wild-type mice. Electrophysiological recordings showed that CNG current was weakly expressed in the olfactory receptor neurons, with decreased cAMP sensitivity in CNGB1 deficient mice. Without CNGB1, the olfactory CNG channel did not target to the olfactory cilia. A small study suggests olfactory function is compromised in people with CNGB1 mutations on both alleles.

Frameshift mutations:

• c.385delC, p.(L129WfsTer148)

Splice site mutationmutations:

Mouse

Dog

A spontaneousframeshift mutation in Cngb1CNGB1 hascausing beencanine progressive retinal atrophy, a condition resembling retinitis pigmentosa, was found in dogs causing recessively inherited progressive retinal degeneration. Thesethe dogsPapillon showeddog earlybreed lossby oftwo rodresearch visiongroups and slowalso photoreceptorin degenerationthe Phalene dog breed. The first test for the canine Cngb1 mutation iswas downstreamlicensed ofto GarpOptiGen andby resultsthe research team lead by Simon Petersen-Jones that discovered the CNGB1 mutation in lack of full-lengthpapillon Cngb1adogs. Gene therapy introducing a normal copy of canine Cngb1aCngb1a into rod photoreceptors resulted in restoration of rod function and preserved retinal structure in Cngb1Cngb1-/- dogs.

Cngb1-X26 is a mouse model missing the full-length protein which was generated by excision of exon 26. The mice show significantly decreased rod function and retinal degeneration. Gene therapy with adeno-associated viral (AAV) vectors carrying CNGB1a cDNA with a rod-specific promoter resulted in retorationrestoration of vision and delay in retinal degeneration in these CNGB1 knockout mice.

Retinitis pigmentosa is a heterogeneous group of inherited ocular diseases characterized by progressive retinal degeneration, causing constriction of visual fields and night blindness, affecting 1 in 3000 to 5000 people. Patients with RP45 typically have night blindness from childhood and loss of peripheral vision has a later onset with RP diagnosis at around 30 years of age and legal blindness around about 60 years of age. RP45 are caused by mutations in CNGB1CNGB1 which are responsible for approximately 4% of autosomal recessive RP.

Retinitis pigmentosa 45 (RP45) was discovered by Bareil et al. (2001) in a consanguineous French family who showed that autosomal recessive segregation of the trait was caused by a missense mutation in exon 30 of the CNGB1CNGB1 gene. Kondo et al. (2004) identified a homozygous splice site mutation in the CNGB1 CNGB1 gene that resulted in a frameshift and truncation of the protein. A homozygous missense mutation at a conserved residue in the CNGB1CNGB1 gene was found to segregate with the disease in a Chinese family by Fu et al. (2013).

Amino acid changes for missense mutations:

• R765C

• R916H

• N986I

• G993V

Splice site mutation:

• c.3444+G>A resulting in a frameshift and skipping exon 32 and truncation of the protein

In olfactory receptor neurons CNG channels generate a receptor current in response to an odorant-induced rise in cAMP. This channel is comprised of CNGA2 which is the principal subunit plus two modulatory subunits, CNGA4 and CNGB1b. CNGB1 -/- deficient mice show decreased olfactory performance and electro-olfactogram responses show a reduced amplitude and decelerated onset and recovery kinetics compared with wild-type mice. Electrophysiological recordings showed that CNG current was weakly expressed in the olfactory receptor neurons, with decreased cAMP sensitivity in CNGB1 deficient mice. Without CNGB1, the olfactory CNG channel did not target to the olfactory cilia.

cGMP stands for cyclic guanosine monophosphate (cGMP) which is a cyclic nucleotide derived from guanosine triphosphate (GTP). Cyclic nucleotide-gated (CNG) channels (CNGs) are activated by binding cGMP or cAMP (cyclic adenosine monophosphate). Changes in intracellular concentrations of cyclic nucleotides are transduced into changes in membrane potential and calcium ion (Ca2+) concentration. In the retinal rod photoreceptor cGMP-gated cation channel, the CNGB1 gene codes for the beta subunit and the CNGA1 gene codes for the alpha subunit.

Genes homologous to human CNGB1 exist in mouse and dog, animals which also serve as models for RP45. Putative homologs of human CNGB1 have also been found in chimpanzee (Pan troglodytes), rhesus macaque (Macaca mulatta), wolf (Canis lupus), domestic cow (Bos Taurus), brown rat (Rattus norvegicus), chicken (Gallus gallus) and nematode (Caenorhabditis elegans).

GARP2 (glutamic acid-rich protein 2) is an alternate isoform formed by alternative splicing of the CNGB1 transcribed RNA. GARP2 is a high affinity rod photoreceptor phosphodiesterase (PDE6)-binding protein that regulates spontaneous activation of rod PDE6, lowering ‘dark nose’ and enabling photoreceptors to function at the single photon detection limit. PDE6 are the sixth family of phosphodiesterases of cyclic nucleotides (PDEs). They are photoreceptor-specific PDEs serving as effector enzymes in vertebrate phototransduction.

CNGB1 is also known as CNG4, GAR1, GARP, RP45, CNCG2, CNCG4, GARP2, RCNC2, RCNCb, CNCG3L, CNGB1BCNGB1a, CNGB1b and RCNCbeta. CNGB1 splice variants GARP1 and GARP2 are expressed in the retina. Splice variant CNGB1b is expressed in the olfactory sensory neurons and other tissues. CNGB1a and CNGB1b are are components of CNG channels.

GARP2 (glutamic acid-rich protein 2) is an alternate isoform formed by alternative splicing of the CNGB1 transcribed RNA. GARP2 is a high affinity rod photoreceptor phosphodiesterase (PDE6)-binding protein that regulates spontaneous activation of rod PDE6, lowering ‘dark nose’ and enabling photoreceptors to function at the single photon detection limit. PDE6 are the sixth family of phosphodiesterases of cyclic nucleotides (PDEs). They are photoreceptor-specific PDEs serving as effector enzymes in vertebrate phototransduction.

CNG channels in rod receptors are composed of three CNGA1 subunits and one CNGB1 (CNGB1a) subunit. The CNGB1b subunit combines with two CNGA2 subunits and one CNGA4 subunit in CNGs of olfactory receptors. CNGA1 can form functional channels on their own but CNGB1 subunits do not. CNGBCNGB1 subunits provide enhanced Ca2+ permeation, modulation by Ca2+-calmodulin and affect nucleotide specificity compared to channels composed of only homomeric CNGA.

GARP2 (glutamic acid-rich protein 2) is an alternate isoform formed by alternative splicing of the CNGB1 transcribed RNA. GARP2 is a high affinity rod photoreceptor phosphodiesterase (PDE6)-binding protein that regulates spontaneous activation of rod PDE6, lowering ‘dark nose’ and enabling photoreceptors to function at the single photon detection limit. PDE6 are the sixth family of phosphodiesterases of cyclic nucleotides (PDEs). They are photoreceptor-specific PDEs serving as effector enzymes in vertebrate phototransduction.

Retinitis pigmentosa is a heterogeneous group of inherited ocular diseases characterized by progressive retinal degeneration, causing constriction of visual fields and night blindness, affecting 1 in 3000 to 5000 people. Patients with RP45 typically have night blindness from childhood and loss of peripheral vision has a later onset with RP diagnosis at around 30 years of age and legal blindness around about 60 years of age. RP45 are caused by mutations in CNGB1 which are responsible for approximately 4% of autosomal recessive RP.

Retinitis pigmentosa is a heterogeneous group of inherited ocular diseases characterized by progressive retinal degeneration, causing constriction of visual fields and night blindness, affecting 1 in 3000 to 5000 people. Mutations in CNGB1 are responsible for approximately 4% of autosomal recessive RP. Retinitis pigmentosa 45 (RP45) was discovered by Bareil et al. (2001) in a consanguineous French family who showed that autosomal recessive segregation of the trait was caused by a missense mutation in exon 30 of the CNGB1 gene. Kondo et al. (2004) identified a homozygous splice site mutation in the CNGB1 gene that resulted in a frameshift and truncation of the protein. A homozygous missense mutation at a conserved residue in the CNGB1 gene was found to segregate with the disease in a Chinese family by Fu et al. (2013).

Cngb1-X26 is a mouse model missing the full-length protein which was generated by excision of exon 26. The mice show significantly decreased rod function and retinal degeneration. Gene therapy with adeno-associated viral (AAV) vectors carrying CNGB1a cDNA with a rod-specific promoter resulted in retoration of vision and delay in retinal degeneration in these CNGB1 knockout mice.

A spontaneous mutation in Cngb1 has been found in dogs causing recessively inherited progressive retinal degeneration. These dogs showed early loss of rod vision and slow photoreceptor degeneration. The canine Cngb1 mutation is downstream of Garp and results in lack of full-length Cngb1a. Gene therapy introducing a normal copy of canine Cngb1a into rod photoreceptors resulted in restoration of rod function and preserved retinal structure in Cngb1-/- dogs.

CNGB1 is also known as CNG4, GAR1, GARP, RP45, CNCG2, CNCG4, GARP2, RCNC2, RCNCb, CNCG3L, CNGB1B and RCNCbeta. GARP2 (glutamic acid-rich protein 2) is an alternate isoform formed by alternative splicing of the CNGB1 transcribed RNA. GARP2 is a high affinity rod photoreceptor phosphodiesterase (PDE6)-binding protein that regulates spontaneous activation of rod PDE6, lowering ‘dark nose’ and enabling photoreceptors to function at the single photon detection limit. CNGB1 splice variants GARP1 and GARP2 are expressed in the retina. Splice variant CNGB1b is expressed in the olfactory sensory neurons and other tissues.

GARP2 (glutamic acid-rich protein 2) is an alternate isoform formed by alternative splicing of the CNGB1 transcribed RNA. GARP2 is a high affinity rod photoreceptor phosphodiesterase (PDE6)-binding protein that regulates spontaneous activation of rod PDE6, lowering ‘dark nose’ and enabling photoreceptors to function at the single photon detection limit. PDE6 are the sixth family of phosphodiesterases of cyclic nucleotides (PDEs). They are photoreceptor-specific PDEs serving as effector enzymes in vertebrate phototransduction.

CNGB1 is also known as CNG4, GAR1, GARP, RP45, CNCG2, CNCG4, GARP2, RCNC2, RCNCb, CNCG3L, CNGB1B and RCNCbeta. The GARP2 (glutamic acid-rich protein 2) is an alternate isoform formed by alternative splicing of the CNGB1 transcribed RNA. GARP2 is a high affinity rod photoreceptor phosphodiesterase (PDE6)-binding protein that regulates spontaneous activation of rod PDE6, lowering ‘dark nose’ and enabling photoreceptors to function at the single photon detection limit. CNGB1 splice variants GARP1 and GARP2 are expressed in the retina. Splice variant CNGB1b is expressed in the olfactory sensory neurons and other tissues.

cGMP stands for cyclic guanosine monophosphate (cGMP) which is a cyclic nucleotide derived from guanosine triphosphate (GTP). Cyclic nucleotidenucleotide-gated channels (CNGs) are activated by binding cGMP or cAMP (cyclic adenosine monophosphate). Changes in intracellular concentrations of cyclic nucleotides are transduced into changes in membrane potential and calcium ion (Ca2+) concentration. In the retinal rod photoreceptor cGMP-gated cation channel, the CNGB1 gene codes for the beta subunit and the CNGA1 gene codes for the alpha subunit. Two CNGB1 subunits combine with two CNGB1 subunits to form a heterotetrameric CNGA2/CNGB1 channel. CNGA1 can form functional channels as homodimers but CNGB1 subunits do not.

CNG channels in rod receptors are composed of three CNGA1 subunits and one CNGB1 subunit. The CNGB1b subunit combines with two CNGA2 subunits and one CNGA4 subunit in CNGs of olfactory receptors. CNGA1 can form functional channels on their own but CNGB1 subunits do not. CNGB subunits provide enhanced Ca2+ permeation, modulation by Ca2+-calmodulin and affect nucleotide specificity compared to channels composed of only homomeric CNGA.

Retinitis pigmentosa is a heterogeneous group of inherited ocular diseases characterized by progressive retinal degeneration, causing constriction of visual fields and night blindness, affecting 1 in 3000 to 5000 people. Mutations in CNGB1 are responsible for approximately 4% of autosomal recessive RP. Retinitis pigmentosa 45 (RP45) was discovered by Bareil et al. (2001) in a consanguineous French family who showed that autosomal recessive segregation of the trait was caused by a missense mutation in exon 30 of the CNGB1 gene. Kondo et al. (2004) identified a homozygous splice site mutation in the CNGB1 gene that resulted in a frameshift and truncation of the protein. A homozygous missense mutation at a conserved residue in the CNGB1 gene was found to segregate with the disease in a Chinese family by Fu et al. (2013).

Human Cyclic Nucleotide Gated Channel Beta 1 (CNGB1) is located on chromosome 16 at cytogenetic location 16q21. The Cyclicgene Nucleotideconsists Gatedof Channel12 Betaexons 1spanning (approximately 11 kb. CNGB1) gene codes for one subunit of a rod photoreceptor cGMP-gated cation channel that in humans helps regulate ion flow into photoreceptors of the eye in response to changes in intracellular cGMP in response to light. CNGB1 gene defects cause a type of blindness called retinitis pigmentosa type 45.

CNGB1 is also known as CNG4, GAR1, GARP, RP45, CNCG2, CNCG4, GARP2, RCNC2, RCNCb, CNCG3L, CNGB1B and RCNCbeta. The GARP2 protein is an alternate isoform formed by alternative splicing of the CNGB1 transcribed RNA. GARP2 is a high affinity rod photoreceptor phosphodiesterase (PDE6)-binding protein that regulates spontaneous activation of rod PDE6, lowering ‘dark nose’ and enabling photoreceptors to function at the single photon detection limit.

CNGB1 is also known as CNG4, GAR1, GARP, RP45, CNCG2, CNCG4, GARP2, RCNC2, RCNCb, CNCG3L, CNGB1B and RCNCbeta. The GARP2 protein is an alternate isoform formed by alternative splicing of the CNGB1 transcribed RNA. GARP2 is a high affinity rod photoreceptor phosphodiesterase (PDE6)-binding protein that regulates spontaneous activation of rod PDE6, lowering ‘dark nose’ and enabling photoreceptors to function at the single photon detection limit.

Retinitis pigmentosa is a heterogeneous group of inherited ocular diseases characterized by progressive retinal degeneration, causing constriction of visual fields and night blindness, affecting 1 in 3000 to 5000 people. Retinitis pigmentosa 45 (RP45) was discovered by Bareil et al. (2001) in a consanguineous French family who showed that autosomal recessive segregation of the trait was caused by a missense mutation in exon 30 of the CNGB1 gene. Kondo et al. (2004) identified a homozygous splice site mutation in the CNGB1 gene that resulted in a frameshift and truncation of the protein. A homozygous missense mutation at a conserved residue in the CNGB1 gene was found to segregate with the disease in a Chinese family by Fu et al. (2013).

cGMP stands for cyclic guanosine monophosphate (cGMP) which is a cyclic nucleotide derived from guanosine triphosphate (GTP). Cyclic nucleotide channels are activated by binding cGMP or cAMP (cyclic adenosine monophosphate). Changes in intracellular concentrations of cyclic nucleotides are transduced into changes in membrane potential and calcium ion (Ca2+) concentration. In the retinal rod photoreceptor cGMP-gated cation channel, the CNGB1 gene codes for the beta subunit and the CNGA1 gene codes for the alpha subunit. Two CNGB1 subunits combine with two CNGB1 subunits to form heteromerica heterotetrameric CNGA2/CNGB1 channelschannel. CNGA1 can form functional channels as homodimers but CNGB1 subunits do not.