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 * Polaris Venture Management Co IV LLC   2. Issuer Name and Ticker or Trading Symbol ACCELERON PHARMA INC [XLRN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director __X__ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O POLARIS VENTURE PARTNERS, 1000 WINTER STREET 3. Date of Earliest Transaction (Month/Day/Year) 06/02/2014 (Street) WALTHAM, MA 02451 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) ___ Form filed by One Reporting Person _X_ 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 06/02/2014   J(1)   198,005 (2) D $ 0 2,621,738 (3) I See Footnote (3)

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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
Polaris Venture Management Co IV LLC C/O POLARIS VENTURE PARTNERS 1000 WINTER STREET WALTHAM, MA 02451		X
POLARIS VENTURE PARTNERS IV LP C/O POLARIS VENTURE PARTNERS 1000 WINTER STREET SUITE 3350 WALTHAM, MA 02451		X
POLARIS VENTURE PARTNERS ENTREPRENEURS FUND IV LP C/O POLARIS VENTURE PARTNERS 1000 WINTER STREET SUITE 3350 WALTHAM, MA 02451		X

Signatures

/s/ John Gannon, Attorney-in-Fact		06/04/2014
**Signature of Reporting Person		Date
/s/ John Gannon, Attorney-in-Fact for Polaris Venture Management Co. IV, L.L.C., general partner of Polaris Venture Partners IV, L.P.		06/04/2014
**Signature of Reporting Person		Date
/s/ John Gannon, Attorney-in-Fact for Polaris Venture Management Co. IV, L.L.C., general partner of Polaris Venture Partners Entrepreneurs Fund IV, L.P.		06/04/2014
**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)	Represents a pro rata distribution without additional consideration by Polaris Venture Partners IV, L.P. ("PVP IV") and Polaris Venture Partners Entrepreneurs Fund IV, L.P. ("PVPE IV" and, together with PVP IV, the "Funds"), to its partners.
(2)	Represents 194,362 shares and 3,643 shares that were held directly by PVP IV and PVPE IV, respectively.
(3)	Represents 2,573,175 shares, 46,568 shares, and 1,995 shares that are held directly by PVP IV, PVPE IV and Polaris Venture Management Co. IV, L.L.C. ("PVM IV"), respectively. PVM IV is the general partner of PVP IV and PVPE IV. PVM IV disclaims beneficial ownership of the Funds' securities and this report shall not be deemed an admission that PVM IV is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of its pecuniary interest, if any, therein. Each of Jonathan A. Flint, Terrance G. McGuire and Alan G. Spoon are the managing members of PVM IV. Each of Messrs. Flint, McGuire and Spoon disclaims beneficial ownership of the Funds' and PVM IV's securities and this report shall not be deemed an admission that any of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their pecuniary interest, if any, therein.

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