NonPatientCell: EFO:0001182 (HEK293 Cells)

GeneFunction: GO:0008233 (Peptidase activity)

GeneAlteration: HEK293 cells were grown and 8 missense mutations were identified and generated by PCR-mutagenesis. The human mutant cDNAs were transfected into the cells using the calcuim-phosphate coprecipitation method and examined.

FunctionalEvidence: When HEK293 cells were transfected with wild-type and mutant human cDNA for PHEX, the resulting cells were subject to immunoblotting to determine the protein levels in both the cell lysate and the media of cells. All the variants and the wild-type showed presence in the lysate at various levels, but C85R, G579R, G579V, S711R, and A720T were all devoid of any secreted protein in the media. Ananlysis of these cells also showed possible rescue by growing transfected cells at 26 C, thus glycosylating and maturing the proteins. The endopeptidase activity of the wild-type and variants were also compared, with D237G and Y317F mutant proteins exhibiting 50–60% of wild-type activity; E581V and S711R also displayed nearly undetectable activity. This displayed that the disease causing mechanism could be related to loss of function of peptidase activity or cellular trafficking. Evidence is found under "Results".

FAVariant1: NM_000444.5:c.253T>C (p.Cys85Arg)

ClinVar: 438549 https://www.ncbi.nlm.nih.gov/clinvar/variation/438549/

FAVariant2: NM_000444.5:c.1735G>A (p.Gly579Arg)

ClinVar: 226119 https://www.ncbi.nlm.nih.gov/clinvar/variation/226119/

FAVariant3: NM_000444.5:c.1736G>T (p.Gly579Val)

ClinVar: 372777 https://www.ncbi.nlm.nih.gov/clinvar/variation/372777/

FAVariant4: NM_000444.5:c.2131A>C (p.Ser711Arg)

CAID: CA412575294 https://reg.clinicalgenome.org/redmine/projects/registry/genboree_registry/by_caid?caid=CA412575294

FAVariant5: NM_000444.5:c.2158G>A (p.Ala720Thr)

CAID: CA412575364 https://reg.clinicalgenome.org/redmine/projects/registry/genboree_registry/by_caid?caid=CA412575364

NonPatientCell: EFO:0001182 (HEK293 Cells)

GeneFunction: GO:0008233 (Peptidase activity)

GeneAlteration: HEK293 cells were grown and 8 missense mutations were identified and generated by PCR-mutagenesis. The human mutant cDNAs were transfected into the cells using the calcuim-phosphate coprecipitation method and examined.

FunctionalEvidence: When HEK293 cells were transfected with wild-type and mutant human cDNA for PHEX, the resulting cells were subject to immunoblotting to determine the protein levels in both the cell lysate and the media of cells. All the variants and the wild-type showed presence in the lysate at various levels, but C85R, G579R, G579V, S711R, and A720T were all devoid of any secreted protein in the media. Ananlysis of these cells also showed possible rescue by growing transfected cells at 26 C, thus glycosylating and maturing the proteins. The endopeptidase activity of the wild-type and variants were also compared, with D237G and Y317F mutant proteins exhibiting 50–60% of wild-type activity; E581V and S711R also displayed nearly undetectable activity. This displayed that the disease causing mechanism could be related to loss of function of peptidase activity or cellular trafficking. Evidence is found under "Results".

FAVariant1: NM_000444.5:c.253T>C (p.Cys85Arg)

ClinVar: 438549 https://www.ncbi.nlm.nih.gov/clinvar/variation/438549/

FAVariant2: NM_000444.5:c.1735G>A (p.Gly579Arg)

ClinVar: 226119 https://www.ncbi.nlm.nih.gov/clinvar/variation/226119/

FAVariant3: NM_000444.5:c.1736G>T (p.Gly579Val)

ClinVar: 372777 https://www.ncbi.nlm.nih.gov/clinvar/variation/372777/

FAVariant4: NM_000444.5:c.2131A>C (p.Ser711Arg)

CAID: CA412575294 https://reg.clinicalgenome.org/redmine/projects/registry/genboree_registry/by_caid?caid=CA412575294

FAVariant5: NM_000444.5:c.2158G>A (p.Ala720Thr)

CAID: CA412575364 https://reg.clinicalgenome.org/redmine/projects/registry/genboree_registry/by_caid?caid=CA412575364

CaseVI-4: Male, 3.5 years, Turkey

CasePresentingHPOs: HP:0004912, HP:0002540, HP:0002970 (Hypophosphatemic rickets, Inability to walk, Genu varum)

HPOsFreeText: -3.76 standard deviation score

CaseNotHPOs: HP:0000083, HP:0002024, HP:0001947 (Renal failure, Malabsorption, Renal tubular acidosis)

NotHPOsFreeText: Other tubulopathies that cause secondary hypophosphatemia, Vitamin D-dependent rickets type 1 and 2

CaseAddInfo: Variant is asserted de novo and confirmed by parental testing, Proband is hemizygous for this mutation

CasePreviousTesting: Calcium levels (9.8 mg/dL), Decreased serum phosphate levels (2.8 mg/dL; reference 3.8-6.5), Elevated serum ALP (925 IU/L; reference 90-325), 25OHD3 levels (35 ng/ml), 1,25(OH)2D3 levels (N/A pg/mL), PTH levels (62.2 ng/L), TPR levels (69.7), Decreased TmP/GFR levels (1.95; reference 2.9-6.1)

CaseGenotypingMethod: Genomic DNA was isolated from peripheral blood leukocytes, amplified, and directly sequenced in all the coding exons and intron-exon boundaries of PHEX. If no mutations were found, FGF23 followed by consecutive analysis of DMP1, ENPP1, CLCN5, SLC34A3 and SLC34A1 was performed. Significance of found mutations was predicted by computational programs and sorted.

Variant: NM_000444.5:c.1217G>T (p.Cys406Phe)

CAID: CA412573391 https://reg.clinicalgenome.org/redmine/projects/registry/genboree_registry/allele?hgvs=NM_000444.5%3Ac.1217G%3ET

gnomAD: Not in gnomAD

CaseVI-4: Male, 3.5 years, Turkey

CasePresentingHPOs: HP:0004912, HP:0002540, HP:0002970 (Hypophosphatemic rickets, Inability to walk, Genu varum)

HPOsFreeText: -3.76 standard deviation score

CaseNotHPOs: HP:0000083, HP:0002024, HP:0001947 (Renal failure, Malabsorption, Renal tubular acidosis)

NotHPOsFreeText: Other tubulopathies that cause secondary hypophosphatemia, Vitamin D-dependent rickets type 1 and 2

CaseAddInfo: Variant is asserted de novo and confirmed by parental testing, Proband is hemizygous for this mutation

CasePreviousTesting: Calcium levels (9.8 mg/dL), Decreased serum phosphate levels (2.8 mg/dL; reference 3.8-6.5), Elevated serum ALP (925 IU/L; reference 90-325), 25OHD3 levels (35 ng/ml), 1,25(OH)2D3 levels (N/A pg/mL), PTH levels (62.2 ng/L), TPR levels (69.7), Decreased TmP/GFR levels (1.95; reference 2.9-6.1)

CaseGenotypingMethod: Genomic DNA was isolated from peripheral blood leukocytes, amplified, and directly sequenced in all the coding exons and intron-exon boundaries of PHEX. If no mutations were found, FGF23 followed by consecutive analysis of DMP1, ENPP1, CLCN5, SLC34A3 and SLC34A1 was performed. Significance of found mutations was predicted by computational programs and sorted.

Variant: NM_000444.5:c.1217G>T (p.Cys406Phe)

CAID: CA412573391 https://reg.clinicalgenome.org/redmine/projects/registry/genboree_registry/allele?hgvs=NM_000444.5%3Ac.1217G%3ET

gnomAD: Not in gnomAD