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Mutations in CDK5RAP2 cause Seckel syndrome.

Yigit G, Brown KE, Kayserili H, Pohl E, Caliebe A, Zahnleiter D, Rosser E, Bögershausen N, Uyguner ZO, Altunoglu U, Nürnberg G, Nürnberg P, Rauch A, Li Y, Thiel CT, Wollnik B - Mol Genet Genomic Med (2015)

Bottom Line: CDK5RAP2 (CEP215) encodes a centrosomal protein which is known to be essential for centrosomal cohesion and proper spindle formation and has been shown to be causally involved in autosomal recessive primary microcephaly.Additionally, we present an intriguing case of possible digenic inheritance in Seckel syndrome: A severely affected child of nonconsanguineous German parents was found to carry heterozygous mutations in CDK5RAP2 and CEP152.This finding points toward a potential additive genetic effect of mutations in CDK5RAP2 and CEP152.

View Article: PubMed Central - PubMed

Affiliation: Institute of Human Genetics, University of Cologne Cologne, Germany ; Center for Molecular Medicine Cologne (CMMC), University of Cologne Cologne, Germany ; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne Cologne, Germany.

ABSTRACT
Seckel syndrome is a heterogeneous, autosomal recessive disorder marked by prenatal proportionate short stature, severe microcephaly, intellectual disability, and characteristic facial features. Here, we describe the novel homozygous splice-site mutations c.383+1G>C and c.4005-9A>G in CDK5RAP2 in two consanguineous families with Seckel syndrome. CDK5RAP2 (CEP215) encodes a centrosomal protein which is known to be essential for centrosomal cohesion and proper spindle formation and has been shown to be causally involved in autosomal recessive primary microcephaly. We establish CDK5RAP2 as a disease-causing gene for Seckel syndrome and show that loss of functional CDK5RAP2 leads to severe defects in mitosis and spindle organization, resulting in cells with abnormal nuclei and centrosomal pattern, which underlines the important role of centrosomal and mitotic proteins in the pathogenesis of the disease. Additionally, we present an intriguing case of possible digenic inheritance in Seckel syndrome: A severely affected child of nonconsanguineous German parents was found to carry heterozygous mutations in CDK5RAP2 and CEP152. This finding points toward a potential additive genetic effect of mutations in CDK5RAP2 and CEP152.

No MeSH data available.


Related in: MedlinePlus

Molecular findings in patient K1600 with Seckel syndrome. (A) Left: Electropherogram of identified heterozygous CDK5RAP2 mutation compared with heterozygous carrier sequence of the mother (K1626) and wild-type sequence of the father (K1872). Right: Electropherogram of identified heterozygous CEP152 mutation compared with heterozygous carrier sequence of the father (K1872) and wild-type sequence of the mother (K1626). (B) Amino acid sequence alignment of CDK5RAP2 proteins of different species shows the highly conserved methionine at position 1396. (C) Schematic view of CDK5RAP2 and CEP152 protein domains. Upper picture: Protein structure of CDK5RAP2 with structural maintenance-of-chromosomes (SMC) domains (blue), γ-tubulin ring complex-binding domain (orange), and pericentrin interaction domain (red). Lower picture: Protein structure of CEP152 with predicted coiled-coil domains (green) and Thr/Ser-phosphorylation sites (red). The positions of the mutations are marked by arrows.
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fig05: Molecular findings in patient K1600 with Seckel syndrome. (A) Left: Electropherogram of identified heterozygous CDK5RAP2 mutation compared with heterozygous carrier sequence of the mother (K1626) and wild-type sequence of the father (K1872). Right: Electropherogram of identified heterozygous CEP152 mutation compared with heterozygous carrier sequence of the father (K1872) and wild-type sequence of the mother (K1626). (B) Amino acid sequence alignment of CDK5RAP2 proteins of different species shows the highly conserved methionine at position 1396. (C) Schematic view of CDK5RAP2 and CEP152 protein domains. Upper picture: Protein structure of CDK5RAP2 with structural maintenance-of-chromosomes (SMC) domains (blue), γ-tubulin ring complex-binding domain (orange), and pericentrin interaction domain (red). Lower picture: Protein structure of CEP152 with predicted coiled-coil domains (green) and Thr/Ser-phosphorylation sites (red). The positions of the mutations are marked by arrows.

Mentions: The heterozygous missense mutation c.4187T>C in CDK5RAP2 was inherited from the patient’s mother (K1626) and is predicted to replace a highly conserved methionine residue (ConSeq score of 6) within one of the conserved SMC domains of CDK5RAP2 with threonine (Fig.5A–C) (Kraemer et al. 2011). The p.Met1396Thr mutation is predicted to be pathogenic by PolyPhen and was neither found in 150 healthy control individuals, nor in the 1,000 Genomes Database, the Exome Variant Server, or the ExAC browser. As we could not detect a second mutation in CDK5RAP2 in this patient, we sequenced ATR (47 exons), CEP152 (27 exons), CENPJ (17 exons), CEP63 (14 exons), and PCNT (47 exons) for additional mutations. Interestingly, we found the heterozygous small indel c.3014_3015delAAinsT in CEP152, inherited from the patient′s father (K1872). The mutation is predicted to cause a frame-shift and a premature stop of translation at amino acid position 1020 (p.Lys1005Ilefs*16), leading to the loss of more than the last third of the CEP152 protein. To exclude any additional larger structural alterations or intronic mutations within CEP152 that might have been acquired from the mother in terms of compound heterozygous inheritance, we verified the presence of two completely functional CEP152 mRNA transcripts on cDNA derived from the patient′s mother (data not shown). We could not obtain fibroblasts from this patient for functional studies in order to prove the postulated additive genetic effect of mutations in CEP152 and CDK5RAP2 and did not receive consent for whole-exome sequencing.


Mutations in CDK5RAP2 cause Seckel syndrome.

Yigit G, Brown KE, Kayserili H, Pohl E, Caliebe A, Zahnleiter D, Rosser E, Bögershausen N, Uyguner ZO, Altunoglu U, Nürnberg G, Nürnberg P, Rauch A, Li Y, Thiel CT, Wollnik B - Mol Genet Genomic Med (2015)

Molecular findings in patient K1600 with Seckel syndrome. (A) Left: Electropherogram of identified heterozygous CDK5RAP2 mutation compared with heterozygous carrier sequence of the mother (K1626) and wild-type sequence of the father (K1872). Right: Electropherogram of identified heterozygous CEP152 mutation compared with heterozygous carrier sequence of the father (K1872) and wild-type sequence of the mother (K1626). (B) Amino acid sequence alignment of CDK5RAP2 proteins of different species shows the highly conserved methionine at position 1396. (C) Schematic view of CDK5RAP2 and CEP152 protein domains. Upper picture: Protein structure of CDK5RAP2 with structural maintenance-of-chromosomes (SMC) domains (blue), γ-tubulin ring complex-binding domain (orange), and pericentrin interaction domain (red). Lower picture: Protein structure of CEP152 with predicted coiled-coil domains (green) and Thr/Ser-phosphorylation sites (red). The positions of the mutations are marked by arrows.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4585455&req=5

fig05: Molecular findings in patient K1600 with Seckel syndrome. (A) Left: Electropherogram of identified heterozygous CDK5RAP2 mutation compared with heterozygous carrier sequence of the mother (K1626) and wild-type sequence of the father (K1872). Right: Electropherogram of identified heterozygous CEP152 mutation compared with heterozygous carrier sequence of the father (K1872) and wild-type sequence of the mother (K1626). (B) Amino acid sequence alignment of CDK5RAP2 proteins of different species shows the highly conserved methionine at position 1396. (C) Schematic view of CDK5RAP2 and CEP152 protein domains. Upper picture: Protein structure of CDK5RAP2 with structural maintenance-of-chromosomes (SMC) domains (blue), γ-tubulin ring complex-binding domain (orange), and pericentrin interaction domain (red). Lower picture: Protein structure of CEP152 with predicted coiled-coil domains (green) and Thr/Ser-phosphorylation sites (red). The positions of the mutations are marked by arrows.
Mentions: The heterozygous missense mutation c.4187T>C in CDK5RAP2 was inherited from the patient’s mother (K1626) and is predicted to replace a highly conserved methionine residue (ConSeq score of 6) within one of the conserved SMC domains of CDK5RAP2 with threonine (Fig.5A–C) (Kraemer et al. 2011). The p.Met1396Thr mutation is predicted to be pathogenic by PolyPhen and was neither found in 150 healthy control individuals, nor in the 1,000 Genomes Database, the Exome Variant Server, or the ExAC browser. As we could not detect a second mutation in CDK5RAP2 in this patient, we sequenced ATR (47 exons), CEP152 (27 exons), CENPJ (17 exons), CEP63 (14 exons), and PCNT (47 exons) for additional mutations. Interestingly, we found the heterozygous small indel c.3014_3015delAAinsT in CEP152, inherited from the patient′s father (K1872). The mutation is predicted to cause a frame-shift and a premature stop of translation at amino acid position 1020 (p.Lys1005Ilefs*16), leading to the loss of more than the last third of the CEP152 protein. To exclude any additional larger structural alterations or intronic mutations within CEP152 that might have been acquired from the mother in terms of compound heterozygous inheritance, we verified the presence of two completely functional CEP152 mRNA transcripts on cDNA derived from the patient′s mother (data not shown). We could not obtain fibroblasts from this patient for functional studies in order to prove the postulated additive genetic effect of mutations in CEP152 and CDK5RAP2 and did not receive consent for whole-exome sequencing.

Bottom Line: CDK5RAP2 (CEP215) encodes a centrosomal protein which is known to be essential for centrosomal cohesion and proper spindle formation and has been shown to be causally involved in autosomal recessive primary microcephaly.Additionally, we present an intriguing case of possible digenic inheritance in Seckel syndrome: A severely affected child of nonconsanguineous German parents was found to carry heterozygous mutations in CDK5RAP2 and CEP152.This finding points toward a potential additive genetic effect of mutations in CDK5RAP2 and CEP152.

View Article: PubMed Central - PubMed

Affiliation: Institute of Human Genetics, University of Cologne Cologne, Germany ; Center for Molecular Medicine Cologne (CMMC), University of Cologne Cologne, Germany ; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne Cologne, Germany.

ABSTRACT
Seckel syndrome is a heterogeneous, autosomal recessive disorder marked by prenatal proportionate short stature, severe microcephaly, intellectual disability, and characteristic facial features. Here, we describe the novel homozygous splice-site mutations c.383+1G>C and c.4005-9A>G in CDK5RAP2 in two consanguineous families with Seckel syndrome. CDK5RAP2 (CEP215) encodes a centrosomal protein which is known to be essential for centrosomal cohesion and proper spindle formation and has been shown to be causally involved in autosomal recessive primary microcephaly. We establish CDK5RAP2 as a disease-causing gene for Seckel syndrome and show that loss of functional CDK5RAP2 leads to severe defects in mitosis and spindle organization, resulting in cells with abnormal nuclei and centrosomal pattern, which underlines the important role of centrosomal and mitotic proteins in the pathogenesis of the disease. Additionally, we present an intriguing case of possible digenic inheritance in Seckel syndrome: A severely affected child of nonconsanguineous German parents was found to carry heterozygous mutations in CDK5RAP2 and CEP152. This finding points toward a potential additive genetic effect of mutations in CDK5RAP2 and CEP152.

No MeSH data available.


Related in: MedlinePlus