FORM 4 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 Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person * KANIA EDWIN M JR   2. Issuer Name and Ticker or Trading Symbol ACCELERON PHARMA INC [XLRN] 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 FLAGSHIP VENTURES, 1 MEMORIAL DRIVE 3. Date of Earliest Transaction (Month/Day/Year) 04/22/2014 (Street) CAMBRIDGE, MA 02142 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction 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) Code V Amount (A) or (D) Price Common Stock 04/22/2014   S   114,746 D $ 35.89 (1) 2,031,974 (2) I See Footnote (2) Common Stock 04/22/2014   S   6,936 D $ 35.89 (1) 122,823 (3) I See Footnote (3) Common Stock 04/23/2014   S   22,349 D $ 33.81 (4) 2,009,625 (2) I See Footnote (2) Common Stock 04/23/2014   S   1,351 D $ 33.81 (4) 121,472 (3) I See Footnote (3) Common Stock 04/24/2014   S   805,905 D $ 31.45 (5) 1,203,720 (2) I See Footnote (2) Common Stock 04/24/2014   S   48,713 D $ 31.45 (5) 72,759 (3) I See Footnote (3) Common Stock               4,867 D

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction 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 (Month/Day/Year)

7. Title and Amount of Underlying Securities (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)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
KANIA EDWIN M JR C/O FLAGSHIP VENTURES, 1 MEMORIAL DRIVE CAMBRIDGE, MA 02142	X

Signatures

/s/ Edwin M. Kania, Jr.		04/24/2014
**Signature of Reporting Person		Date

Explanation of Responses:

*	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).
(1)	The price reported in Column 4 is a weighted average price. These shares were disposed of by Applied Genomic Technology Capital Fund, L.P. ("AGTC Fund") and AGTC Advisors Fund, L.P. ("AGTC Advisors") in multiple transactions on the Transaction Date at prices ranging from $35.00 to $36.86, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, and/or the staff of the U.S. Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnotes (1), (4), and (5) to this Form 4. All of the sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by AGTC Fund and AGTC Advisors on December 16, 2013.
(2)	Represents shares held by AGTC Fund. NewcoGen Group, Inc. ("NewcoGen Inc.") is the general partner of AGTC Partners, L.P., which is the general partner of AGTC Fund. NewcoGen Inc. is a wholly-owned subsidiary of Flagship Ventures Management, Inc. Noubar B. Afeyan, Ph.D. and Mr. Kania are the directors of Flagship Venture Management, Inc. and, as such, have shared voting and dispositive power over all shares held by AGTC Fund. Each of Mr. Kania and Dr. Afeyan disclaim beneficial ownership over the shares held by AGTC Fund except to the extent of his pecuniary interest therein.
(3)	Represents shares held by AGTC Advisors. NewcoGen Group, Inc. ("NewcoGen Inc.") is the general partner of AGTC Partners, L.P., which is the general partner of AGTC Advisors. NewcoGen Inc. is a wholly-owned subsidiary of Flagship Ventures Management, Inc. Noubar B. Afeyan, Ph.D. and Mr. Kania are the directors of Flagship Venture Management, Inc. and, as such, have shared voting and dispositive power over all shares held by AGTC Advisors. Each of Mr. Kania and Dr. Afeyan disclaim beneficial ownership over the shares held by AGTC Advisors except to the extent of his pecuniary interest therein..
(4)	The price reported in Column 4 is a weighted average price. These shares were disposed of by AGTC Fund and AGTC Advisors in multiple transactions on the Transaction Date at prices ranging from $33.15 to $35.26, inclusive.
(5)	The price reported in Column 4 is a weighted average price. These shares were disposed of by AGTC Fund and AGTC Advisors in multiple transactions on the Transaction Date at prices ranging from $30.50 to $33.52, inclusive.

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