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A 15-month-old girl is referred for ophthalmologic and neurologic follow-up by her pediatrician. The child has shown a failure to thrive, is microcephalic, exhibits myoclonic jerks, delayed psychomotor development, visual disturbance and seizures. Analysis of fibroblasts from the skin by electron microscopy confirms the presence of fingerprint inclusion bodies. Elevated levels of dolichol are found in the urine. Normally, dolichol is associated with which cellular process:

A. Sulfation in the trans compartment of the Golgi
B. O-linked glycosylation in the medial compartment of the Golgi
C. O-linked glycosylation in the cis compartement of the Golgi
D. N-linked glycosylation in the endoplasmatic reticulum
E. Sorting of proteins to the lysosome from the TGN

 

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In all probability, this girl suffers from I-cell disease, which is clinically similar to Hurler's syndrome (the latter is notorious for causing corneal clouding).

In I-cell disease (I for Inclusion bodies, as described in the question stem), the deficit lies upon the enzyme N-acetyl-glucosaminyl-phosphotransferase, which belongs to the superfamily of dolichol. As its name indicates, its role is to add mannose-6-phosphate residues to the N-terminal of peptides, in order for them to be signaled for degradation into the lysosomes. Once this enzyme is deficient, peptides that would otherwise be degraded, eventually accumulate within inclusion bodies, attributing to the cells the characteristic microscopic appearance for the disease.

So, the correct answer must be D.
 

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A 15-month-old girl is referred for ophthalmologic and neurologic follow-up by her pediatrician. The child has shown a failure to thrive, is microcephalic, exhibits myoclonic jerks, delayed psychomotor development, visual disturbance and seizures. Analysis of fibroblasts from the skin by electron microscopy confirms the presence of fingerprint inclusion bodies. Elevated levels of dolichol are found in the urine. Normally, dolichol is associated with which cellular process:

A. Sulfation in the trans compartment of the Golgi
B. O-linked glycosylation in the medial compartment of the Golgi
C. O-linked glycosylation in the cis compartement of the Golgi
D. N-linked glycosylation in the endoplasmatic reticulum
E. Sorting of proteins to the lysosome from the TGN
I didnt even know what Dolichol is (will look up later), and glad it didnt come out on my Step 1... However, since it ends in "ol", I assumed it to be an alcohol. Knowing that Steroids, Lipids, and alcohols have a portion metabolized by the SER, option D.) was my safest guess. Sometimes one has to use street smarts to nail a Q or two. :p
 
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