GALC Genetics tail (NIH ClinVar tally), GalactosylSph (=psychosine, GalSph), Assay of GalactosylSph, Krabbe’s Disease start

NIH ClinVar Variation type / Clinical significance (GALC tail)

• KD-genic
• Deletions

NIH ClinVar — Variation type:

• Deletion (127)
• Duplication (68)
• Indel (9)
• Insertion (67)
• Single nucleotide (749)

NIH ClinVar — Clinical significance:

• Conflicting interpretations (55)
• Benign (129)
• Likely benign (293)
• Uncertain significance (203)
• Likely pathogenic (163)
• Pathogenic (172)

Galactosylsph (=psychosine, GalSph)

field	content
distribution / location	(Marshall, 2018 #1302) Psychosine was found to have a robust distribution, elevated in the white matter and substantia nigra of all patients. (Abdelkarim, 2018 #1301) In KD, psychosine is found not only in lipid rafts33, but also in lysosomes and in the extra-lysosomal environment (cytoplasm or/and extracellular matrix) 54,55

Disease state comparison

	nGD	PD	Altered? / Correction	Krabbe disease
CSF	(Schiffmann, 1997 #1304) Trend! n=12, patients 0.202 nmol/ml (0.041-0.688), VS control: 0.09 nmol/ml (0.034-0.186). not statistically significant	간접증거 [Tottori, ambroxol p7 (CSF), p8 (serum)]	(Marshall, 2018 #1302) psychosine: trend! postmortem brain, fig1, 겨우 q에서만 p=0.05에 근접. SN: ↑, caudate: =, WM: seems ↑ but no	(Orsini, 2016 #1305) Blood, new born, highly consistently ↑ (Marshall, 2018 #1302) See left! (Li, 2019 #1189), carmofur, animal model brain (fig 3M)
Cortex	Total Cortical Psychosine, P = 0.0554 [Tottori univ] 증가이유 0.10 (CSF GalSph, P=0.0034**) Psychosine (pmol/mg protein) [statistical analysis result, GME = WM+GM of cortex: ↑ (24.37±9.05 vs 15.7319±2.41) d=0.94 [in-house-Niigata univ] [amygdala] cohen's d of 0.72 (excel) (the same d from nM and ng/mL) [occipital] cohen's d of 0.19 (excel)
Tottori GD comparison	HC 396.9±236.2 vs PD: 835.±825.6 (p=0.04) (nM) HC 1833±1090 vs PD 385.4±381.1 (P=0/04) (ng/mL) GD patients vs Disease control 불명 (↓ GBA → ↓ Ceramide 그러면 GalCer도 줄어야 하는데, Tottori에 증가 경향인걸 보면 보상으로 느는듯 ↑ GalSph)

aSyn / Krabbe relationship

Krabbe’s disease patients sometimes have ‘parkinsonian’ characteristics (though hard to ascertain clinically given their young age), and aSyn pathology has been found in their brains at autopsy (Hatton et al, 2022; https://doi.org/10.1093/brain/awac002). Inhibiting acid ceramidase would prevent the conversion of (Abdelkarim et al., 2018, PMID: 30127535).

psychosine forms hydrophilic clusters and binds the C-terminus of aSyn → promotes aggregation of a-syn in NSC34 motor-neuron cells (Abdelkarim et al., 2018, PMID 30127535) 그런데 PD에서 psychosine 안 증가이기 때문에 이 증거는 별 의미 X

psychosine → promotes fibrillization of a-syn (in vitro) ((Smith, 2014 #1303) 역시 PD에서 psychosine 안 증가이기 때문에 이 증거는 별 의미 X

Tottori 보면 확실히 GlcSph 보다 detection 잘 되고 GD에서 증가폭 크네.

Assay of GalactosylSph

(Matsumoto, 2022 #2152) LCMS (Otake-san) normal human (brain, CSF, plasma) 모두 에서 잼.

GlcSph and GalSph in normal human CSF were 1.07 and 9.44 pg/ml, respectively.

assay LLOQs were 0.1 pg/mL in CSF, and 0.03 ng/mL in plasma. A 200 μL aliquot of CSF and an 80 μL aliquot of plasma are required for quantification. Additionally, the blood contamination test is recommended using 50 μL CSF if possible.

Krabbe’s Disease (=Globoid cell leukodystrophy)

More than 200 GALC gene mutations that cause Krabbe disease have been identified (대개는 homoz인데, 혹시 heteroz 일 수도 있다).

The most common mutation in affected individuals of European ancestry (often called 30-kb del) deletes a large segment of the GALC gene. Other mutations insert additional DNA building blocks (nucleotides) into the GALC gene, delete a small number of nucleotides from the gene, or replace single nucleotides with incorrect nucleotides.

Pathway:

• ↓ GALC activity
• ↓ galactosylceramide
• ↑ psychosine (forms during the production of myelin and is quickly broken down by galactosylceramidase.)
• ↑ damage to myelin-forming cells, ↑ demyelination, myelin, movement, eating, impaired development, and seizures.

Galactosylceramide 이 원래 myelin 의 성분이긴 하지만, 축적된 psychosine 때문에 demyelination 오나보다.

Some individuals develop symptoms of Krabbe disease in childhood, adolescence, adulthood (late-onset Krabbe disease).

The severity of the condition may also be affected by the presence of additional common variations (polymorphisms) in the GALC gene that affect the activity of the galactosylceramidase enzyme.

(Marshall, 2018 #2200) fig1 (M, N, O, P) 뇌의 전영역에서 (late-onset KD 도 WM, Caudate 에선 증가로 매우 evident).

(Marshall, 2018 #2200) fig1 (e, f, g, h): ↑ LB-like, aSyn aggregation in (late-onset KD 도 WM, Caudate 에선 증가로 보임) postmortem brain Twitcher mouse model.

(Smith, 2014 #2199) {Abdelkarim, #2201} genetic correction of GALC deficiency completely / genetic KO of a-syn reduces, but does not completely

(Li, 2019 #1189), carmofur, Twi: GALC^+/- mice (Krabbe disease model) Twi/FDH: GALC, ASAH mice

Very low enzyme activity (0%-5% of normal activity) is observed in all individuals with Krabbe disease who are symptomatic. (대개는 enzyme activity in leukocytes (or skin fibroblast) 로 확진함.)

Uncertain Spans

location	transcription	uncertainty
Smith 2014 / Abdelkarim 2018 / cell row	genetic KO of a-syn reduces, but does not completely	reads as written; the sentence is clipped at the visible boundary.