Statement of Changes in Beneficial Ownership (4)

FORM 4 [ X ] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response... 0.5
	Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

1. Name and Address of Reporting Person ^* Hohneker John	2. Issuer Name and Ticker or Trading Symbol Dimension Therapeutics, Inc. [ DMTX ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __ X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below)
(Last) (First) (Middle) C/O DIMENSION THERAPEUTICS, INC., 840 MEMORIAL DRIVE 4TH FLOOR	3. Date of Earliest Transaction (MM/DD/YYYY) 11/7/2017
(Street) CAMBRIDGE, MA 02139 (City) (State) (Zip)	4. If Amendment, Date Original Filed (MM/DD/YYYY)	6. Individual or Joint/Group Filing (Check Applicable Line) _ X _ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security (Instr. 3)	2. Trans. Date	2A. Deemed Execution Date, if any	3. Trans. Code (Instr. 8)		4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
1.Title of Security (Instr. 3)	2. Trans. Date	2A. Deemed Execution Date, if any	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)

*Table II - Derivative Securities Beneficially Owned ( e.g.* , puts, calls, warrants, options, convertible securities)**
1. Title of Derivate Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Trans. Date	3A. Deemed Execution Date, if any	4. Trans. Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Derivate Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Trans. Date	3A. Deemed Execution Date, if any	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)			11. Nature of Indirect Beneficial Ownership (Instr. 4)
Stock Option (Right to Buy)	$4.60	11/7/2017		D			38000	⁽¹⁾	1/17/2027	Common Stock	38000	⁽¹⁾	0	D

Explanation of Responses:

(1)

This stock option, which vests annually over three years, beginning January 18, 2017, subject to the director's continued service on the Board, was assumed by Ultragenyx Pharmaceutical Inc. ("Ultragenyx"), and converted in accordance with the exchange ratio as set forth in the Agreement and Plan of Merger (the "Merger Agreement"), dated October 2, 2017, between the Issuer, Ultragenyx and Mystic River Merger Sub Inc., a direct, wholly-owned subsidiary of Ultragenyx.

Reporting Owners
Reporting Owner Name / Address	Relationships
Reporting Owner Name / Address	Director	10% Owner	Officer	Other
Hohneker John C/O DIMENSION THERAPEUTICS, INC. 840 MEMORIAL DRIVE 4TH FLOOR CAMBRIDGE, MA 02139	X

Signatures
/s/ Mary Thistle, as Attorney-in-Fact for John Hohneker		11/7/2017
^** Signature of Reporting Person		Date

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note:	File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.