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NYS Krabbe Newborn Screening Referrals

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Presentation on theme: "NYS Krabbe Newborn Screening Referrals"— Presentation transcript:

1 NYS Krabbe Newborn Screening Referrals
Carlos A. Saavedra-Matiz, M.D. Newborn Screening Program Wadsworth Center New York State Department of Health NYMAC Albany, NY June 4-5, 2012

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3 INVALID SPECIMENS

4 96-WELL PLATES ARE LABELED
FOR USE EACH DAY

5 SPECIMENS ARE BUNDLED FOR REPEATS

6 Knud (Haraldsen) Krabbe
Krabbe Disease Krabbe K: A new familial, infantile form of diffuse brain sclerosis. Brain 1916; 39: 74. Galactocerebrosidase Deficiency Globoid Cell Leukodystrophy (GLD) Galactosylceramidase Deficiency GALC Deficiency Knud (Haraldsen) Krabbe ( )

7 Krabbe Disease “Inherited metabolic disorder”
Autosomal recessive; Pan-ethnic Carrier frequency ~ 1:150; Incidence 1:100,000 Deficiency of the lysosomal enzyme galactocerebrosidase (GALC) Mutations in GALC Decreased ability to degrade galactolipids Failure of myelination in the CNS and PNS Pathology is limited to nervous system Progressive neurologic deterioration and death May be under-diagnosed Cerebral palsy Multiple sclerosis At least two forms Source: Wenger, et al. In Scriver, 2001.

8 Krabbe Disease – Clinical Features
Infantile form (85-90%) - Normal for first few months; develops feeding difficulties - Developmental delay, irritability and spasticity before 6 months of age - Death usually before 2 years Late-Onset form (10-15%) - Variable clinical course from 6 months - 50 years - Weakness, vision loss, intellectual regression

9 Add assay solution reagent and incubate
New York State Assay Punch 3-mm specimen Add assay solution reagent and incubate 19 hours Up to 24 96-well plates are tested each day Quench reaction (50/50 MeOH/EtAc) Liquid / liquid extraction (EtAc/H20) Remove organic phase (150 μL) Dry plates 1 hour Re-dissolve in MS suitable solvent (80/20 MeOH/H20) Analyze samples, 1.5 minutes per sample Calculate activity/sample, daily mean activity, % of daily mean act/sample

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11 KRABBE DISEASE Artificial Substrate Product Internal Standard

12 Krabbe Screening: Cutoffs and Testing Algorithm
All specimens tested for GALC activity < 20% of daily mean > 20% of daily mean Retested in duplicate (or more) Average of 3 samples ≤ 12% Average of 3 samples > 12% DNA testing 1 or more mutations No mutations Screen Positive Referral Screen Negative

13 umol/L/hr Daily Mean 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0 0.36 12.0 11.6 11.3 10.9 10.6 10.3 10.0 9.7 9.5 9.2 9.0 8.8 8.6 8.4 8.2 8.0 7.8 7.7 7.5 7.3 7.2 0.37 12.3 11.9 11.2 9.3 7.9 7.6 7.4 0.38 12.7 11.5 8.3 8.1 0.39 13.0 12.6 12.2 11.8 11.1 10.8 10.5 9.8 9.1 8.9 8.7 8.5 0.40 13.3 12.9 12.5 12.1 11.4 0.41 13.7 13.2 12.8 12.4 11.7 0.42 14.0 13.5 13.1 10.2 0.43 14.3 13.9 13.4 11.0 9.6 0.44 14.7 14.2 13.8 10.7 9.4 0.45 15.0 14.5 14.1 13.6 0.46 15.3 14.8 14.4 0.47 15.7 15.2 10.4 0.48 16.0 15.5 0.49 16.3 15.8 0.50 16.7 16.1 15.6 0.51 17.0 16.5 15.9 14.6 0.52 17.3 16.8 14.9 0.53 17.7 17.1 16.6 15.1 0.54 18.0 17.4 16.9 16.4 15.4 0.55 18.3 17.2 16.2 0.56 18.7 18.1 17.5 0.57 19.0 18.4 17.8 0.58 19.3 17.6 0.59 19.7 17.9 0.60 20.0 19.4 18.8 18.2

14 If activity ≤ 12% then perform DNA Testing
Mutated gene: GALC Chromosome 14 17 exons 75+ known mutations (finding many unknown variants) 30 kb deletion is most common Multiple activity-attenuating polymorphisms Reduce activity by 80-90% Wenger, et al. In Scriver, 2001.

15 p.I546T p.Y551S p.R168C RT-FRET-PCR c.602C>T (p.R168C) c.694G>A (p.694G>A) c.1637T>C (p.I546T) c.809G>A (p.G270D) c.1538C>T (p.T513M) c.1652A>C (p.Y551S) c.1424delA PCR-Agarose Gel 30Kb Deletion 7.4Kb Deletion

16 Molecular Analysis of GALC
Reduce number of false positive screens Predict phenotype (?) Method: Agarose gel for 2 common deletions 30 kb 7 kb Probes for 7 common mutations/polymorphisms Sequence all 17 exons and Promoter Region 30 kb deletion Normal Mutant p.T513M (1538C>T)

17 DNA SEQUENCE ANALYSIS Exon 15 Gly559ValfsX10 (c.1675insT)

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19 New York State Specialty Care Programs
Strong Memorial Hospital HSA 3 HSA 5 Crouse Memorial Hospital HSA 2 Albany Medical Center HSA 1 HSA 4 Women and Children’s Hospital of Buffalo HSA 6 Westchester Medical Center HSA 8 Mount Sinai Montefiore SUNY at Stony Brook HSA 7

20 Referred infants - Risk categories
GALC ACTIVITY RISK CATEGORY nmol/hr/mg protein (future: 0.2) High (future: 0.2 – 0.35) Moderate (future: eliminate) Low > 0.5 (future: >0.35) No Risk Note that these categories have been evaluated by the New York State Krabbe Consortium, and will be changed in near future. Conf EA Dr. David A. Wenger at Jefferson Medical College Courtesy of Dr. P. Duffner

21 Referred infants: After NBS Screening
Confirmatory Enzyme Analysis (Dr. David A. Wenger) Consult with Geneticist/Child Neurologist Draw blood sample-HLA, Identity (WC) If enzyme test affirms Krabbe disease likely.. Exam CSF protein MRI Nerve conduction, BAER, VER, and other studies recommend periodic evaluation, depending on dx lab enzyme activity level. A point system is used, if 4 or more points: Consideration given to receive cord blood treatment

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23 High Risk Children p.R168C_g.30 Kb Del // p.I546T_p.X670Qext42 [TP]
9.9% 0.01 nmol/hr/mg protein p.R168C_g.30Kb Del // p.R168C_g.30 Kb Del [TP] 10.9% 0.05 nmol/hr/mg protein p.A5P _p.D232N_p.Y303C // p.A5P_p.D232N_p.Y303C 6.1% 0.06 nmol/hr/mg protein p.A5P_p.D232N_p.Y303C / p.I546T // p.D556fsX1 8.3% 0.12 nmol/hr/mg protein p.A5P / p.D232N / p.Y303C // p.H375QfsX3 / p.I546T 9.6% 0.07 nmol/hr/mg protein 6. p.A247T / p.I546T // p.A5P/ p.T96A / p.D232N 5.0% 0.09 nmol/hr/mg protein

24 High Risk Children 7. c.-123_128del6_p.L618S // p.L618S
9.1% 0.12 nmol/hr/mg protein p.R168C_g.30Kb Del // p.R168C_g.30Kb Del 7.6% 0.02 nmol/hr/mg protein [parents refused TP; symptomatic] 9. p.R168C_g.30Kb Del // p.G360DfsX2 [TP] 5.6% 0.12 nmol/hr/mg protein p.M101V_c G>C_p.A625T // p.M309V_p.I546T 4.7% 0.03 nmol/hr/mg protein c.147G>C_p.I546T // p.K85E_p.I546T 6.2% nmol/hr/mg protein p.A5P _p.D232N_p.Y303C // p.T452I 4.9% 0.05 nmol/hr/mg protein

25 Moderate Risk Children
%ADM nmol/hr/mg protein Allele 1 Allele 2 6.7% 0.16 p.A5P_p.D232N_p.Y303C 9.1% 0.17 c.535-1G>A p.R53Q_p.I546T 9.7% 0.18 p.A5P_p.T96A_p.D232N 7.9% p.M101V_c G>A_p.A625T p.M101V_c G>A_p.A625 11.9% 9.4% p.A247T_p.I546T 8.0% 0.20 c.-123_128del6_p.L618S 11.5% p.A5P_p.D232N_p.T513M p.R168C_p.I546T p.G95S 10.4% p.R168C_g.30Kb Del 10.0% p.G537R_c G>A_p.A625T 8.5% 0.23 p.I546T_p.Y551S 8.3% 0.24 p.D445A_p.L618S p.L618S 9.2% 0.25 9.5% p.I546T_p.D556fsX1 10.3% 7.1% 0.26 8.9% 0.28 9.8% 0.29 p.P73L_p.I546T p.A5P_p.D232N_p.Y298del_p.I571T 10.9% 0.30

26 NOVEL MUTATIONS Referral Group (02/10/12) p.R53Q (x7) p.M101V (x16)
p.N151S (x3) p.R63C (x8) p.R53X p.D94D (x8) p.W115R (x2) p.G559D p.L616P p.P239H p.D556X (x2) p.A44V p.A209E p.A209T p.P73L (x5) p.V320M (x5) p.E60K (x2) p.M309V p.G360DfsX2 c C>G (x17) p.X670Q (x3) p.K83E (x2) p.D445A c.*12C>A p.R111X (x2) p.A290T p.Y601X p.H375QfsX3 p.Met1? p.R63C (x8) p.A356S p.S353R p.L263X

27 Allele Carrier Freq Allele Freq p.I546T 0.88 0.58 p.R168C 0.61 0.37 p.D232N 0.40 0.23 p.T96A 0.24 0.13 g.30KbDel 0.15 0.08 p.Y303C 0.12 0.07 p.A625T 0.06 0.03

28 Krabbe Genotype (Additional Description)
p.R168C-p.I546T Homozygous (Polys Only - No Referral) p.I546T Homozygous (Polys Only - No Referral) (Updated ) p.R168C-p.I546T Homozygous Enz Act <8% (Mom's only phased) c.-196T>C-c.-7G>C-p.A5P-p.T96A-p.D232N / c.-196T>C-c.-7G>C-p.A5P-p.T96A-p.D232N (Phased only Mom) c.-196T>C-c.-7G>C-p.A5P-p.D232N-p.Y303C Homozygous (Not phased) (Created ) p.R168C-p.I546T / p.R168C-p.I546T-c.*12G>A Enz Act <8% c.147G>C-p.I546T / p.R168C-p.I546T (090420) c.147G>C-p.I546T / p.I546T c.-335G>A / c.282C>T (p.D94D) / p.R168C-p.I546T / p.I546T c.-335G>A / p.R168C-p.I546T / p.I546T c.-335G>A-p.I546T / p.I546T c.-511C>T-p.I546T / p.I546T c A>G-p.I546T / p.R168C-p.I546T (Created ) c.-196T>C-c.-7G>C-p.A5P-p.D232N / p.I546T Polys Only (Not a referral – Created ) c.-196T>C-c.-7G>C-p.A5P-p.D232N ?-/ p.I546T Polys Only Enz Act <8% (Referral) One parent phased (Created ) c.-196T>C / c.-85C>T / c.-7G>C / p.A5P / p.R168C / p.D232N / p.I546T c.-335G>A / c.-59T>A / p.I546T Homozygous (Polys Only) (Created ) c.-335G>A-c.282C>T(p.D94D)-p.I546T / p.I546T (Polys Only-Updated090305) c.-335G>A-c.282C>T(p.D94D)-p.I546T // p.R168C-p.I546T (V3 = 3rd Case) c.-335G>A-c.282C>T(p.D94D)-p.I546T // p.R168C-p.I546T (V4-4thCase-Polys Only-Updated090205) c.-335G>A-c.282C>T(p.D94D)-p.I546T / p.R168C-p.I546T c.-335G>A-c.282C>T(p.D94D)-p.I546T / p.R168C-p.I546T (V2 = 2nd Case) c.-7G>C / p.A5P/ p.D232N / p.I546T/ p.R168C-p.I546T p.Arg168Cys_g.30-Kb Del // c.-335G>A_p.Gly360AspfsX2 (Created ) c.-196T>C--c.-7G>C--p.A5P--p.D232N--p.Y303C // p.A247T--p.I546T p.R380W-p.I546T // p.F491L-p.I546T p.V320M_p.R380W_p.I546T // p.I546T (Created ) c.-335G>A-p.E60K-p.I546T // c.-196T>C-c.-7G>C-p.A5P-p.T96A-p.D232N (Created ) p.I546T / p.A625T c.-335G>A - p.P73L(c.218C>T) - p.I546T/ p.R168C-g.30KbDel c.-196T>C-c.-7G>C-p.A5P-p.D232N-p.T452S-p.K568X / p.I546T c.-196T>C-c.-7G>C-p.A5P-p.T96A-p.D232N / p.M101V-c G>C-p.A625T c.-196T>C_c.-7G>C_p.A5P_p.D232N_p.T452S_p.G559Vfsx10 // p.V320M-p.Ile546Thr (Modified ) c.-196T>C_c.-7G>c_p.A5P_p.T96A_p.D232N // p.A563E (Created ) c.-196T>C--c.-115T>G--c.-7G>C--p.Ala5Pro--p.Arg53X--p.Asp232Asn // c.-196T>C--c.-7G>c--p.Ala5Pro--p.Thr96Ala--p.Asp232Asn c.-196T>C_c.-7G>C_p.Ala5Pro_p.Thr96Ala_p.Asp232Asn / c.-196T>C_c.-7G>C_p.Ala5Pro_p.Asp232Asn_p.Ser353Arg (Created ) c.-196T>C_c.-7G>c_p.A5P_p.T96A_p.D232N // c.-196T>C_c.-7G>c_p.D232N_p.Tyr303Cys (Created ) c.-196T>C-c.-7G>C-p.A5P-p.T96A-p.D232N / c.-335G>A-p.A247T-p.I546T c.-196T>C_c.-7G>c_p.A5P_p.D232N_p.Y303C // p.I546T_p.D556fsX1 (Created ) c.-196T>C_c.-7G>C_p.Ala5Pro_p.Asp232Asn_p.Thr452Ser_p.Gly559ValfsX10 // p.Val320Met_p.Ile546Thr p.I546-p.D556XT / c.-7G>C-p.A5P-p.D232N-p.Y303C c.-348C>T--c.-196T>C--c.-7G>C--p.A5P--p.D232N--p.Y303C / p.I546T / p.H375QX3 p.R168C-g.30KbDel / p.I546T (Phased) (Created ) p.R168C-g.30KbDel / p.I546T p.R168C-g.30KbDel / p.R168C-p.I546T p.A209E / p.I546T c.-335G>A / c.-196T>C / c.-7G>C / p.A5P-p.D232N-p.I546T / p.A247T / p.I546T c.-196T>C-c.-7G>C-p.A5P-p.D232N-p.A290T / p.I546T p.A44V-p.I546T / p.R168C-p.I546T p.A563E / p.I546T c.-335G>A-p.A247T-p.I546T // p.R168C-p.I546T p.A356S_p.I546T // p.R168C_p.I546T (Created ) p.R111X-p.I546T // p.R168C-p.I546T (Phased) (Created ) p.R168C-p.I546T / p.I546T p.R168C_p.I546T / p.I546T p.R204X // p.Ile546Thr p.R204X-p.I546T / p.I546T (Not phased) (Created ) p.R53Q--p.I546T // p.I546T p.N151S_p.I546T / c.-335G>A_p.I546T (Created ) p.N151S-p.I546T / p.R168C-p.I546T (Created ) p.N279I-p.I546T / p.R168C-p.I546T p.R168C-p.D171V-p.I546T // p.R168C-p.I546T p.D445A-p.L618S / p.L618S p.G268S-p.I546T // p.R168C-p.I546T (Created ) c.G307R / p.R168C-p.I546T (Created ) p.I546T-p.G559D / p.I546T (Created ) c.-335G>A_p.G95S // p.R168C_p.I546T (Created ) p.G95S / p.R168C-p.I546T (Created ) p.K83E-p.I546T / p.I546T p.Leu263X_p.Ile546Thr // p.Arg168Cys_p.Ile546Thr (Created ) p.L616P-p.I546T // p.R168C-p.I546T (Created ) p.M101V-c G>C-p.A625T / p.I546T (Not Phased) p.M101V-c G>C-p.A625T / p.I546T (Phased) p.M101V-c G>C-p.A625T / p.R168C-p.I546T p.M101V-c G>C-p.A625T / p.R168C-p.I546T (System) p.Met1?-p.I546T / p.I546T p.M101V-c G>C-p.A625T / p.R168C-p.I546T (Updated ) c.-335G>A - p.P73L(c.218C>T) - p.I546T / p.I546T c.-335G>A - p.P73L - p.I546T / p.R168C - p.I546T c.-335G>A - p.P73L - p.I546T / p.R168C - p.I546T (Second identical genotype-update090203) c.-335G>A-p.F498S-p.I546T / p.R168C-p.I546T (Created090622) Krabbe Genotype (Additional Description) p.R168C-p.I546T Homozygous (Polys Only - No Referral) p.I546T Homozygous (Polys Only - No Referral) (Updated ) p.R168C-p.I546T Homozygous Enz Act <8% (Mom's only phased) c.-196T>C-c.-7G>C-p.A5P-p.T96A-p.D232N / c.-196T>C-c.-7G>C-p.A5P-p.T96A-p.D232N (Phased only Mom) c.-196T>C-c.-7G>C-p.A5P-p.D232N-p.Y303C Homozygous (Not phased) (Created ) p.R168C-p.I546T / p.R168C-p.I546T-c.*12G>A Enz Act <8% c.147G>C-p.I546T / p.R168C-p.I546T (090420) c.147G>C-p.I546T / p.I546T c.-335G>A / c.282C>T (p.D94D) / p.R168C-p.I546T / p.I546T c.-335G>A / p.R168C-p.I546T / p.I546T c.-335G>A-p.I546T / p.I546T c.-511C>T-p.I546T / p.I546T c A>G-p.I546T / p.R168C-p.I546T (Created ) c.-196T>C-c.-7G>C-p.A5P-p.D232N / p.I546T Polys Only (Not a referral – Created ) c.-196T>C-c.-7G>C-p.A5P-p.D232N ?-/ p.I546T Polys Only Enz Act <8% (Referral) One parent phased (Created ) c.-196T>C / c.-85C>T / c.-7G>C / p.A5P / p.R168C / p.D232N / p.I546T c.-335G>A / c.-59T>A / p.I546T Homozygous (Polys Only) (Created ) c.-335G>A-c.282C>T(p.D94D)-p.I546T / p.I546T (Polys Only-Updated090305) c.-335G>A-c.282C>T(p.D94D)-p.I546T // p.R168C-p.I546T (V3 = 3rd Case) c.-335G>A-c.282C>T(p.D94D)-p.I546T // p.R168C-p.I546T (V4-4thCase-Polys Only-Updated090205) c.-335G>A-c.282C>T(p.D94D)-p.I546T / p.R168C-p.I546T c.-335G>A-c.282C>T(p.D94D)-p.I546T / p.R168C-p.I546T (V2 = 2nd Case) c.-7G>C / p.A5P/ p.D232N / p.I546T/ p.R168C-p.I546T p.Arg168Cys_g.30-Kb Del // c.-335G>A_p.Gly360AspfsX2 (Created ) c.-196T>C--c.-7G>C--p.A5P--p.D232N--p.Y303C // p.A247T--p.I546T p.R380W-p.I546T // p.F491L-p.I546T p.V320M_p.R380W_p.I546T // p.I546T (Created ) c.-335G>A-p.E60K-p.I546T // c.-196T>C-c.-7G>C-p.A5P-p.T96A-p.D232N (Created ) p.I546T / p.A625T c.-335G>A - p.P73L(c.218C>T) - p.I546T/ p.R168C-g.30KbDel c.-196T>C-c.-7G>C-p.A5P-p.D232N-p.T452S-p.K568X / p.I546T c.-196T>C-c.-7G>C-p.A5P-p.T96A-p.D232N / p.M101V-c G>C-p.A625T c.-196T>C_c.-7G>C_p.A5P_p.D232N_p.T452S_p.G559Vfsx10 // p.V320M-p.Ile546Thr (Modified ) c.-196T>C_c.-7G>c_p.A5P_p.T96A_p.D232N // p.A563E (Created ) c.-196T>C--c.-115T>G--c.-7G>C--p.Ala5Pro--p.Arg53X--p.Asp232Asn // c.-196T>C--c.-7G>c--p.Ala5Pro--p.Thr96Ala--p.Asp232Asn c.-196T>C_c.-7G>C_p.Ala5Pro_p.Thr96Ala_p.Asp232Asn / c.-196T>C_c.-7G>C_p.Ala5Pro_p.Asp232Asn_p.Ser353Arg (Created ) c.-196T>C_c.-7G>c_p.A5P_p.T96A_p.D232N // c.-196T>C_c.-7G>c_p.D232N_p.Tyr303Cys (Created ) c.-196T>C-c.-7G>C-p.A5P-p.T96A-p.D232N / c.-335G>A-p.A247T-p.I546T c.-196T>C_c.-7G>c_p.A5P_p.D232N_p.Y303C // p.I546T_p.D556fsX1 (Created ) c.-196T>C_c.-7G>C_p.Ala5Pro_p.Asp232Asn_p.Thr452Ser_p.Gly559ValfsX10 // p.Val320Met_p.Ile546Thr p.I546-p.D556XT / c.-7G>C-p.A5P-p.D232N-p.Y303C c.-348C>T--c.-196T>C--c.-7G>C--p.A5P--p.D232N--p.Y303C / p.I546T / p.H375QX3 p.R168C-g.30KbDel / p.I546T (Phased) (Created ) p.R168C-g.30KbDel / p.I546T p.R168C-g.30KbDel / p.R168C-p.I546T p.A209E / p.I546T c.-335G>A / c.-196T>C / c.-7G>C / p.A5P-p.D232N-p.I546T / p.A247T / p.I546T c.-196T>C-c.-7G>C-p.A5P-p.D232N-p.A290T / p.I546T p.A44V-p.I546T / p.R168C-p.I546T p.A563E / p.I546T c.-335G>A-p.A247T-p.I546T // p.R168C-p.I546T p.A356S_p.I546T // p.R168C_p.I546T (Created ) p.R111X-p.I546T // p.R168C-p.I546T (Phased) (Created ) p.R168C-p.I546T / p.I546T p.R168C_p.I546T / p.I546T p.R204X // p.Ile546Thr p.R204X-p.I546T / p.I546T (Not phased) (Created ) p.R53Q--p.I546T // p.I546T p.N151S_p.I546T / c.-335G>A_p.I546T (Created ) p.N151S-p.I546T / p.R168C-p.I546T (Created ) p.N279I-p.I546T / p.R168C-p.I546T p.R168C-p.D171V-p.I546T // p.R168C-p.I546T p.D445A-p.L618S / p.L618S p.G268S-p.I546T // p.R168C-p.I546T (Created ) c.G307R / p.R168C-p.I546T (Created ) p.I546T-p.G559D / p.I546T (Created ) c.-335G>A_p.G95S // p.R168C_p.I546T (Created ) p.G95S / p.R168C-p.I546T (Created ) p.K83E-p.I546T / p.I546T p.Leu263X_p.Ile546Thr // p.Arg168Cys_p.Ile546Thr (Created ) p.L616P-p.I546T // p.R168C-p.I546T (Created ) p.M101V-c G>C-p.A625T / p.I546T (Not Phased) p.M101V-c G>C-p.A625T / p.I546T (Phased) p.M101V-c G>C-p.A625T / p.R168C-p.I546T p.M101V-c G>C-p.A625T / p.R168C-p.I546T (System) p.Met1?-p.I546T / p.I546T p.M101V-c G>C-p.A625T / p.R168C-p.I546T (Updated ) c.-335G>A - p.P73L(c.218C>T) - p.I546T / p.I546T c.-335G>A - p.P73L - p.I546T / p.R168C - p.I546T c.-335G>A - p.P73L - p.I546T / p.R168C - p.I546T (Second identical genotype-update090203) c.-335G>A-p.F498S-p.I546T / p.R168C-p.I546T (Created090622)

29 KRABBE DISEASE GALC DATABASE
New York State Newborn Screening Program Wadsworth Center, New York State Department of Health GALC Database Summary Data Variant/Mutation Data Patients/Clinical Data GALC Sequence Data Search Submit Data Krabbe Disease GALC Gene Krabbe Disease Links References Disclaimer How to Cite this Database Contact Site Map Mission Statement: To provide a resource for states considering screening for Krabbe disease Database Version Last Update # hits

30 Variant/Mutation Data
Summary Data Page Krabbe Disease Links Search & Download Page News Page Variant/Mutation Data How to Cite this Database Page Patient/Clinical Data Krabbe Disease GALC Database HomePage Contributors Page GALC Sequence Page References Page Contact Info Page How to Submit Data Sequence Alignment Page Data Dictionary Page

31 ONGOING PROJECTS Sequence analysis of confirmed cases
Sequence analysis of Whites, Blacks, Hispanics, Asians Cloning of most common alleles for expression studies

32 GALC p.Lys612Asp (c.1836delA) / chr14q31.3-32.12 Del
B M/D B M D M/D B

33 p.R168C (E5) p.I546T (E17)

34 Mutations in the galactocerebrosidase (GALC) gene cause globoid cell leukodystrophy (GLD or Krabbe disease). Krabbe is an autosomal recessive disease. This newborn has two mutations, three polymorphisms and two promoter region variants in the GALC gene. One copy each of the p.Arg63Cys (c.187C>T) and p.Tyr303Cys (c.908A>G) mutations were detected. The phenotype associated with the novel p.Arg63Cys mutation is unknown; however, a previous report of a mutation in the same amino acid, p.Arg63His, in two adolescent Krabbe sisters (in a different genetic background) suggests that p.Arg63Cys may be associated with the juvenile-onset form of the disease. The p.Tyr303Cys (c.908A>G) mutation has been associated with the late-onset form of the disease in a different genetic background. In general, late-onset forms of Krabbe are heterogeneous with a slow progression of clinical signs. One copy each of the allelic variants p.Ala5Pro (c.13G>C), p.Asp232Asn (c.694G>A) and p.Ile546Thr (c.1637T>C) were also detected. The p.Ala5Pro variant and p.Asp232Asn polymorphism virtually always occur together: p.Ala5Pro is not expected to affect GALC activity since it is located in the leader peptide, which is removed during processing and p.Asp232Asn reduces enzyme activity by 30-40%. The p.Ile546Thr polymorphism reduces GALC enzyme activity by 60-70%. In addition, this infant has one copy each of the c.-196T>C and c.-7G>C promoter region variants. No transcriptional effect is expected from these variants since they are not located at any of the putative GALC regulatory element binding sites. One allele in this baby consists of p.Arg63Cys_p.Ile546Thr and the second allele consists of c.-196T>C_c.-7G>C_p.Ala5Pro_p.Asp232Asn_p.Tyr303Cys. The reduction in GALC enzyme activity from each allele has not been quantified and the expected clinical course of this baby cannot be predicted. Each parent carries one of these alleles thus future pregnancies have a recurrence risk of 25%. Due to this genotype and the low GALC enzyme activity, referral to a metabolic specialist for evaluation, follow-up and genetic counseling is recommended. This test was performed using the polymerase chain reaction (PCR) to amplify across the breakpoint of the 30-kb deletion, the most common GALC gene mutation causing the classic infantile form of Krabbe disease. The PCR products were analyzed by agarose gel electrophoresis. Further analysis was completed by PCR followed by fluorescence-based sequence analysis of the promoter, all 17 exons, and intron/exon boundaries of the GALC gene.

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