Initial capitalization of foreign surnames when starting a sentence
Solution 1:
Fortunately, The Chicago Manual of Style (16th edition) deals with this question on page 388:
8.5 Names with particles. Many names include particles such as de, d', de la, von, van, and ten. Practice with regard to capitalization and spacing the particles varies widely, and confirmation should be sought in a biographical dictionary or other authoritative source. When the surname is used alone, the particle is usually retained, capitalized or lowercased and spaced as in the full name (though always capitalized when beginning a sentence). [emphasis added]
So, following Chicago, the correct sentence is, "De Bernezan entered the room."
The variation in capitalization you found on the De Vries Wikipedia page is explained by the Chicago rule for Dutch names used in an English context (page 390):
8.10 Dutch names. In English usage, the particles van, van den, ter, and the like are lowercased when full names are given but usually capitalized when only the last name is used.
Johannes van Keulen; Van Keulen
Pieter van den Keere; Van den Keere
Vincent van Gogh; Van Gogh
Gerard ter Borch; Ter Borch
Solution 2:
The case of a reference list of an academic paper will be covered in my answer. (Sorry, not directly relevant to the OP, but this question is redirected here.)
APA Style says, according to APA Style Blog: How to Capitalize Author Names in APA Style, in a reference list, lowercase is retained:
de Haan, A. D., Deković, M., & Prinzie, P. (2012). Longitudinal impact of parental and adolescent personality on parenting. Journal of Personality and Social Psychology, 102, 189–199. doi:10.1037/a0025254
APA Style agrees with the Chicago Manual for the sentence beginning. After a colon capitalization is necessary, too. Thus:
- De Haan, Deković, and Prinzie (2012) studied the impact of parental and adolescent personality on parenting.
- Recently, researchers have explored the impact of personality on parenting: De Haan, Deković, and Prinzie (2012) used longitudinal analyses to untangle the effects.