Reviewer's report 
 Localization of ABCG5 and ABCG8 proteins in human liver, gall bladder and intestine Title: 
 2  9 July 2004 Version: Date: 
 Folkert Kuipers Reviewer: 
Reviewer's report: 
General This paper provides important new information on the localization of the sterolin proteins 
ABCG5 and ABCG8 in human liver, gallbladder and intestine, making use of new peptide-generated 
polyclonal rabbit-antisera on subfractionated liver membrane fractions and immunohistochemistry. It 
is shown that in liver the proteins are present in membranes with a predominant apical 
co-localization, confirmed in liver by significant co-localization with MRP2,but that the two proteins 
also have an expression pattern that is independent from each other. With respect to the latter, it is 
surprising that in liver ABCG8 showed a more intracellular distribution pattern whereas in the intestine ABCG5 showed a more diffuse pattern. This may indicate separate functions of both proteins in these organs. Of specific relevance is the demonstration of ABCG5/8 protein expression 
in the gallbladder, suggesting that this organ is able to modulate bile composition with respect to 
cholesterol content. A surprising finding is the apparent lack of glycosylation of the human proteins, in contrast to the situation in rodents. The potential implications hereof remain elusive for the moment. 
------------------------------------------------------------------------------- 
Major Compulsory Revisions (that the author must respond to before a decision on publication can be reached) 
None 
------------------------------------------------------------------------------- Minor Essential Revisions (such as missing labels on figures, or the wrong use of a term, which the author can be trusted to correct) 
page 12, line 10: "In the liver, cells lining the hepatobiliary tracks (should be "tracts")". Sentence 
apparently not yet finished because both hepatocytes and ductular cells were mentioned earlier. ------------------------------------------------------------------------------- Discretionary Revisions (which the author can choose to ignore) 
-ABCG5/8 activity in the gallbladder, if also present in mice, may explain partly divergent results 
from mouse studies in which either gallbladder bile or hepatic bile was used to establish the effects of gene disruption/pharmacological gene induction on bile composition. Authors may want to comment on this issue. 
-Presence of ABCG8 alone in bile ductular cells is surprising but not further commented on-do the 
authors have any suggestion for a physiological function ? 
 Accept after minor essential revisions What next?: 
 An article of importance in its field Level of interest: 
 Acceptable Quality of written English: 
 No Statistical review: 
Declaration of competing interests: 
None 
Reviewer's report 
 Localization of ABCG5 and ABCG8 proteins in human liver, gall bladder and intestine Title: 
 2  9 July 2004 Version: Date: 
 Folkert Kuipers Reviewer: 
Reviewer's report: 
General This paper provides important new information on the localization of the sterolin proteins 
ABCG5 and ABCG8 in human liver, gallbladder and intestine, making use of new peptide-generated 
polyclonal rabbit-antisera on subfractionated liver membrane fractions and immunohistochemistry. It 
is shown that in liver the proteins are present in membranes with a predominant apical 
co-localization, confirmed in liver by significant co-localization with MRP2,but that the two proteins 
also have an expression pattern that is independent from each other. With respect to the latter, it is 
surprising that in liver ABCG8 showed a more intracellular distribution pattern whereas in the intestine ABCG5 showed a more diffuse pattern. This may indicate separate functions of both proteins in these organs. Of specific relevance is the demonstration of ABCG5/8 protein expression 
in the gallbladder, suggesting that this organ is able to modulate bile composition with respect to 
cholesterol content. A surprising finding is the apparent lack of glycosylation of the human proteins, in contrast to the situation in rodents. The potential implications hereof remain elusive for the moment. 
------------------------------------------------------------------------------- 
Major Compulsory Revisions (that the author must respond to before a decision on publication can be reached) 
None 
------------------------------------------------------------------------------- Minor Essential Revisions (such as missing labels on figures, or the wrong use of a term, which the author can be trusted to correct) 
page 12, line 10: "In the liver, cells lining the hepatobiliary tracks (should be "tracts")". Sentence 
apparently not yet finished because both hepatocytes and ductular cells were mentioned earlier. ------------------------------------------------------------------------------- Discretionary Revisions (which the author can choose to ignore) 
-ABCG5/8 activity in the gallbladder, if also present in mice, may explain partly divergent results 
from mouse studies in which either gallbladder bile or hepatic bile was used to establish the effects of gene disruption/pharmacological gene induction on bile composition. Authors may want to comment on this issue. 
-Presence of ABCG8 alone in bile ductular cells is surprising but not further commented on-do the 
authors have any suggestion for a physiological function ? 
 Accept after minor essential revisions What next?: 
 An article of importance in its field Level of interest: 
 Acceptable Quality of written English: 
 No Statistical review: 
Declaration of competing interests: 
None 
Please review this paper.
user
Reviewer's report 
 Localization of ABCG5 and ABCG8 proteins in human liver, gall bladder and intestine Title: 
 2  9 July 2004 Version: Date: 
 Folkert Kuipers Reviewer: 
Reviewer's report: 
General This paper provides important new information on the localization of the sterolin proteins 
ABCG5 and ABCG8 in human liver, gallbladder and intestine, making use of new peptide-generated 
polyclonal rabbit-antisera on subfractionated liver membrane fractions and immunohistochemistry. It 
is shown that in liver the proteins are present in membranes with a predominant apical 
co-localization, confirmed in liver by significant co-localization with MRP2,but that the two proteins 
also have an expression pattern that is independent from each other. With respect to the latter, it is 
surprising that in liver ABCG8 showed a more intracellular distribution pattern whereas in the intestine ABCG5 showed a more diffuse pattern. This may indicate separate functions of both proteins in these organs. Of specific relevance is the demonstration of ABCG5/8 protein expression 
in the gallbladder, suggesting that this organ is able to modulate bile composition with respect to 
cholesterol content. A surprising finding is the apparent lack of glycosylation of the human proteins, in contrast to the situation in rodents. The potential implications hereof remain elusive for the moment. 
------------------------------------------------------------------------------- 
Major Compulsory Revisions (that the author must respond to before a decision on publication can be reached) 
None 
------------------------------------------------------------------------------- Minor Essential Revisions (such as missing labels on figures, or the wrong use of a term, which the author can be trusted to correct) 
page 12, line 10: "In the liver, cells lining the hepatobiliary tracks (should be "tracts")". Sentence 
apparently not yet finished because both hepatocytes and ductular cells were mentioned earlier. ------------------------------------------------------------------------------- Discretionary Revisions (which the author can choose to ignore) 
-ABCG5/8 activity in the gallbladder, if also present in mice, may explain partly divergent results 
from mouse studies in which either gallbladder bile or hepatic bile was used to establish the effects of gene disruption/pharmacological gene induction on bile composition. Authors may want to comment on this issue. 
-Presence of ABCG8 alone in bile ductular cells is surprising but not further commented on-do the 
authors have any suggestion for a physiological function ? 
 Accept after minor essential revisions What next?: 
 An article of importance in its field Level of interest: 
 Acceptable Quality of written English: 
 No Statistical review: 
Declaration of competing interests: 
None 
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